CN211627459U - Pulse width adjustable ultrasonic square wave transmitting circuit - Google Patents
Pulse width adjustable ultrasonic square wave transmitting circuit Download PDFInfo
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- CN211627459U CN211627459U CN202020152169.XU CN202020152169U CN211627459U CN 211627459 U CN211627459 U CN 211627459U CN 202020152169 U CN202020152169 U CN 202020152169U CN 211627459 U CN211627459 U CN 211627459U
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- 239000003990 capacitor Substances 0.000 claims abstract description 25
- 238000004146 energy storage Methods 0.000 claims abstract description 23
- 230000005284 excitation Effects 0.000 claims abstract description 9
- 238000002955 isolation Methods 0.000 claims abstract description 9
- 230000005540 biological transmission Effects 0.000 claims description 9
- 230000001960 triggered effect Effects 0.000 claims description 4
- 230000007547 defect Effects 0.000 abstract description 3
- 230000002349 favourable effect Effects 0.000 abstract description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 2
- 230000003014 reinforcing effect Effects 0.000 abstract description 2
- 238000013016 damping Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 235000012431 wafers Nutrition 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 238000002604 ultrasonography Methods 0.000 description 2
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000009659 non-destructive testing Methods 0.000 description 1
- 230000010355 oscillation Effects 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
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Abstract
The utility model discloses a pulsewidth adjustable ultrasonic wave square wave transmitting circuit, include: the energy converter comprises an energy converter chip, a control signal input unit, a leading edge excitation circuit and a trailing edge excitation circuit, wherein a square wave control signal is input into the control signal input unit; the front edge excitation circuit comprises a first MOS tube and an energy storage capacitor, the grid electrode of the first MOS tube is electrically connected with the control signal input unit, the drain electrode of the first MOS tube is electrically connected with the energy storage capacitor, and a first isolation diode is electrically connected between the energy storage capacitor and the energy transducer chip; the back edge excitation circuit comprises a second MOS tube, the grid electrode of the second MOS tube is electrically connected with the control signal input unit, and a second isolation diode is electrically connected between the drain electrode of the second MOS tube and the transducer chip. The utility model discloses a square wave control signal has replaced traditional sharp pulse control signal, can produce the ultrasonic wave at square wave control signal's forward position and back porch homoenergetic, and the ultrasonic wave of production can superpose the reinforcing, and emission efficiency improves, the frequency is purer, can improve the SNR, is favorable to the defect to be detected.
Description
Technical Field
The utility model relates to a nondestructive test technical field especially indicates an ultrasonic wave square wave transmitting circuit of pulsewidth adjustable.
Background
In nondestructive testing, ultrasonic testing is a safe, effective and convenient testing mode. Most of the emission waveforms of the conventional ultrasonic flaw detectors are sharp pulses, negative pulses are generally adopted for emission, the front edge is steep, the back edge is attenuated through a damping circuit, and the steep back edge is difficult to have generally, as shown in fig. 1. Depending on the characteristics of the ultrasonic probe (piezoelectric transducer), it is the leading or trailing edge of the pulse, rather than the level, that excites the wafer to generate the ultrasonic waves. Therefore, as shown in the figure, the excitation efficiency of the leading edge of the sharp pulse is relatively high, and the trailing edge is a slowly-varying signal, so that the amplitude of the generated pulse ultrasonic wave is relatively small, and the ultrasonic wave generated by the leading edge cannot play a role in enhancing.
If square wave emission is adopted, the piezoelectric wafers are excited along two edges, if the pulse width is just 1/2 of the oscillation period of the wafers, the intensity of the excited ultrasonic wave is maximum, the frequency components are relatively pure, generally, the emitted wave is enhanced, the echo is also enhanced, and the defect detection is facilitated.
SUMMERY OF THE UTILITY MODEL
The utility model provides an ultrasonic wave square wave transmitting circuit has solved among the prior art ultrasonic wave transmission wave form back edge not precipitous, can not arouse stronger ultrasonic technical problem.
The technical scheme of the utility model is realized like this: an ultrasonic square wave transmitting circuit with adjustable pulse width, comprising:
a transducer chip for outputting a transmit voltage;
the control signal input unit is used for inputting a square wave control signal output by a control signal output end of the programmable logic device into the control signal input unit;
the leading edge excitation circuit comprises a first MOS tube which is triggered and conducted at the leading edge of the square wave control signal and an energy storage capacitor, wherein the grid electrode of the first MOS tube is electrically connected with the control signal input unit, the drain electrode of the first MOS tube is electrically connected with the energy storage capacitor, and a first isolation diode is electrically connected between the energy storage capacitor and the energy transducer chip;
and the back edge excitation circuit comprises a second MOS tube which is triggered and conducted at the back edge of the square wave control signal, the grid electrode of the second MOS tube is electrically connected with the control signal input unit, and a second isolation diode is electrically connected between the drain electrode of the second MOS tube and the transducer chip.
Preferably, the programmable logic device is an FGPA or a CPLD.
As a preferable technical solution, the control signal input unit includes an SN74AHCT125 buffer, an a pin of the SN74AHCT125 buffer is electrically connected to the control signal output terminal of the programmable logic device, and a Y pin of the SN74AHCT125 buffer is electrically connected to the gate of the first MOS transistor and the gate of the second MOS transistor.
As a preferred technical solution, the Y pin of the SN74AHCT125 buffer is electrically connected to the gate of the first MOS transistor and the gate of the second MOS transistor through a set of differential circuits, respectively.
As a preferred technical solution, the first MOS transistor is an N-channel MOS transistor.
As a preferred technical solution, the second MOS transistor is a P-channel MOS transistor.
As a preferred technical scheme, one end of the energy storage capacitor is electrically connected with a charging power supply through a first current limiting resistor.
The beneficial effects of the utility model reside in that: the utility model discloses a programmable logic device produces square wave control signal, and square wave pulse width is adjustable, and the regulation precision can reach 10 ns.
The utility model discloses a square wave control signal has replaced traditional sharp pulse control signal, can produce the ultrasonic wave at square wave control signal's forward position and back porch homoenergetic, and the ultrasonic wave of production can superpose the reinforcing, and emission efficiency improves, the frequency is purer, can improve the SNR, is favorable to the defect to be detected.
In conventional circuits, in order to change the steepness of the trailing edge of the sharp pulse, relays are usually used to switch high power resistors to change the damping. Because ultrasonic emission is the high pressure, and the instantaneous power is bigger, consequently is used for doing damped resistance volume and can not be too little, and in addition the volume of relay hardly reduces for ultrasonic emission circuit's volume becomes very big, the utility model discloses in got rid of damping switching circuit, made the circuit board miniaturization of ultrasonic flaw detector, and then reduced the whole quick-witted size of ultrasonic flaw detector.
The utility model discloses in, second MOS pipe and second are kept apart the diode under the drive of square wave control signal back porch, and the electric charge on the transducer chip is let out rapidly for the back porch of launching the wave form is precipitous.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.
FIG. 1 is a waveform diagram of a square wave control signal, a transmitting circuit output waveform, and a prior art top pulse in an embodiment of the present invention;
fig. 2 is a schematic circuit diagram according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, rather than all embodiments, and the descriptions of these embodiments are used to help understanding the present invention, but do not constitute a limitation of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative efforts belong to the protection scope of the present invention.
In the description of the present application, it is to be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present application and for simplicity in description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated in a particular manner, and are not to be construed as limiting the present application. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.
As shown in fig. 1 and fig. 2, an ultrasonic square wave transmitting circuit with adjustable pulse width includes an SN74AHCT125 buffer, an a pin of the SN74AHCT125 buffer is electrically connected to a control signal output terminal of a programmable logic device, and a Y pin of the SN74AHCT125 buffer is electrically connected to a gate of a MOS transistor Q1 and a gate of a MOS transistor Q2.
The programmable logic device is an FGPA or CPLD, the FGPA or CPLD outputs square wave control signals, and the SN74AHCT125 buffer is used for enhancing the driving capability of the signals, so that the edges of the transmitted waveforms are steeper.
In order to strengthen the edge, the transmitting circuit adopts two groups of differential circuits, the differential circuit consisting of C3 and R1 is electrically connected to the grid of the MOS tube Q1, and the differential circuit consisting of C2 and R2 is electrically connected to the grid of the MOS tube Q2.
The MOS transistor Q1 is an N-channel MOS transistor, and the MOS transistor Q2 is a P-channel MOS transistor.
The drain of the MOS tube Q1 is electrically connected with an energy storage capacitor C1, one end of the energy storage capacitor C1 is electrically connected with a 150V direct-current power supply through a current-limiting resistor R5, isolation diodes D3 and D6 are electrically connected between the other end of the energy storage capacitor C1 and the transducer chip C4, and the other end of the energy storage capacitor C1 is grounded through a current-limiting resistor R7 and a diode D1. In this embodiment, C4 is the equivalent capacitance of the transducer chip.
The drain electrode of the MOS tube Q2 is electrically connected with the isolation diodes D4 and D5 between the transducer chip C4 and the drain electrode of the MOS tube Q2.
In this embodiment, the MOS transistor Q1 is used for leading edge control, and the MOS transistor Q2 is used for trailing edge control. The main function of the diode D1 is to shorten the charging time of C1, increasing the maximum repetition frequency of the system. The primary function of D6 and D3 is to isolate C1 from the transducer chip C4 and to withstand the voltage differential between the two capacitances. D4 and D5 mainly play a role in ensuring unidirectional conduction isolation.
When the emission voltage is 150V, C1 ≈ 1.0uF, the equivalent capacitance of the piezoelectric crystal C4 ≈ 700pF, R7 ≈ 500 Ω, R6 ═ 10 Ω, and R3 ≈ 200k Ω.
The control signal (signal with high level of 3.3V and low level of 0V) from the FPGA module is driven by the MOS transistor Q1 to become a signal with high level of +5V and low level of 0V, the maximum current of the MOS transistor Q1 depends on the emission voltage and the current limiting resistor R7, and I is U/R7 is 0.3A. The descending speed of the front edge is determined by the front edge control MOS tube Q1.
Since the storage capacitor C1 does not need to be fully discharged, the role of R5 is to ensure that the current through the MOS transistor Q1 does not exceed its limiting current.
When the leading edge control MOS tube Q1 is conducted, the positive voltage end of the fully charged energy storage capacitor C1 is grounded through Q1, the energy storage capacitor C1 applies-150V voltage to the transducer chip C4 through D6 and D3, and the transducer chip C4 instantly drops to the emission voltage close to-150V. Because the capacitance of the energy storage capacitor C1 is about 1000 times that of the energy storage capacitor C4, the voltage on the energy storage capacitor C1 is basically unchanged, and a negative pulse appears on the transducer chip C4.
When the trailing edge of the control signal arrives, Q1 turns off, Q2 turns on, D6 and D3 turn off, and the charge on transducer chip C4 discharges through D4, D5, Q2 and R6. The minimum discharge constant is: T-R6C 4-7 ns. The average current I is UC4/T is 15A.
If C1 needs to be fully discharged, its minimum discharge constant is: t' R6C1 ═ 10us > T ═ 7 ns. It can be seen that since the equivalent capacitor C4 of the transducer chip has much smaller capacitance than the energy storage capacitor C1, the discharge time is greatly shortened, the trailing edge time is much smaller, and the trailing edge is steeper.
In this embodiment, the repetition transmission frequency is not lower than 1200hz (prf) under the condition of ensuring that the voltage error of each transmission is allowed to be ± 3%.
Since the pulse width of the ultrasonic emission is determined by the width of the emission control signal, the control of the emission pulse width can be easily realized by controlling the width of the emission control signal, and the control precision of the emission control signal depends on the control precision of the emission control signal. The time of the ultrasound emission depends on the time of the occurrence of the leading edge of the emission control signal, and the phase of the emitted ultrasound is controlled by controlling the time (or phase) of the occurrence of the leading edge of the emission control signal.
In this embodiment, because each emission does not require the charge in the energy storage capacitor C1 to be completely discharged, that is, the charge that is not discharged after each charge is completed can be used next time, the emission efficiency of the system is greatly improved. The charging resistor of the energy storage capacitor C1 can select a larger resistance value, so that the power consumed by the charging resistor of the transmitting part is reduced, a low-power resistor can be selected, the integration level is improved, and the power requirement on a transmitting high-voltage power supply is also reduced.
The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. An ultrasonic square wave transmitting circuit with adjustable pulse width, which is characterized by comprising:
a transducer chip for outputting a transmit voltage;
the control signal input unit is used for outputting a square wave control signal to the control signal output end of the programmable logic device and inputting the square wave control signal into the control signal input unit;
the leading edge excitation circuit comprises a first MOS tube which is triggered and conducted at the leading edge of the square wave control signal and an energy storage capacitor, wherein the grid electrode of the first MOS tube is electrically connected with the control signal input unit, the drain electrode of the first MOS tube is electrically connected with the energy storage capacitor, and a first isolation diode is electrically connected between the energy storage capacitor and the energy transducer chip;
and the back edge excitation circuit comprises a second MOS tube which is triggered and conducted at the back edge of the square wave control signal, the grid electrode of the second MOS tube is electrically connected with the control signal input unit, and a second isolation diode is electrically connected between the drain electrode of the second MOS tube and the transducer chip.
2. The pulse width tunable ultrasonic square wave transmission circuit of claim 1, wherein: the programmable logic device is a FGPA or a CPLD.
3. The pulse width tunable ultrasonic square wave transmission circuit of claim 1, wherein: the control signal input unit comprises an SN74AHCT125 buffer, an A pin of the SN74AHCT125 buffer is electrically connected with a control signal output end of the programmable logic device, and a Y pin of the SN74AHCT125 buffer is electrically connected with a grid electrode of the first MOS tube and a grid electrode of the second MOS tube.
4. The pulse width tunable ultrasonic square wave transmission circuit of claim 3, wherein: and the Y pin of the SN74AHCT125 buffer is electrically connected with the grid electrode of the first MOS tube and the grid electrode of the second MOS tube through a group of differential circuits respectively.
5. The pulse width tunable ultrasonic square wave transmission circuit of claim 1, wherein: the first MOS tube is an N-channel MOS tube.
6. The pulse width tunable ultrasonic square wave transmission circuit of claim 1, wherein: the second MOS tube is a P-channel MOS tube.
7. The pulse width tunable ultrasonic square wave transmission circuit of claim 1, wherein: one end of the energy storage capacitor is electrically connected with the charging power supply through the first current limiting resistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020152169.XU CN211627459U (en) | 2020-02-04 | 2020-02-04 | Pulse width adjustable ultrasonic square wave transmitting circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202020152169.XU CN211627459U (en) | 2020-02-04 | 2020-02-04 | Pulse width adjustable ultrasonic square wave transmitting circuit |
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| CN211627459U true CN211627459U (en) | 2020-10-02 |
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| CN202020152169.XU Active CN211627459U (en) | 2020-02-04 | 2020-02-04 | Pulse width adjustable ultrasonic square wave transmitting circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116448216A (en) * | 2023-05-29 | 2023-07-18 | 浙江美仪智能传感技术有限公司 | Program-controlled ultrasonic liquid level meter transmitting circuit, receiving circuit and ranging system |
-
2020
- 2020-02-04 CN CN202020152169.XU patent/CN211627459U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116448216A (en) * | 2023-05-29 | 2023-07-18 | 浙江美仪智能传感技术有限公司 | Program-controlled ultrasonic liquid level meter transmitting circuit, receiving circuit and ranging system |
| CN116448216B (en) * | 2023-05-29 | 2024-03-22 | 浙江美仪智能传感技术有限公司 | Program-controlled ultrasonic liquid level meter transmitting circuit, receiving circuit and ranging system |
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| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| PE01 | Entry into force of the registration of the contract for pledge of patent right |
Denomination of utility model: A Pulse Width Adjustable Ultrasonic Square Wave Emission Circuit Effective date of registration: 20231013 Granted publication date: 20201002 Pledgee: Hangzhou United Rural Commercial Bank Limited by Share Ltd. Baoshan Branch Pledgor: Hangzhou Ouba Technology Co.,Ltd. Registration number: Y2023980060900 |
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| PE01 | Entry into force of the registration of the contract for pledge of patent right |