A method of differential driving of an ultrasonic transducer

Abstract

The application provides a differential driving method of an ultrasonic transducer, and relates to the technical field of ultrasonic transducers, and comprises the following steps: S1, circuit connection: connecting circuit elements, setting six control pins on a control chip, and connecting each control pin to a corresponding position in the circuit, S2, transmitting and receiving ultrasonic waves by taking UT1 as a transmitting end and UT2 as a receiving end. The differential driving method of the ultrasonic transducer gives a negative pulse through fire1_n and fire2_n, differentially drives the transducer, increases the amplitude of the received electric signal, can receive a stronger electric signal in the case that the working voltage is low and the signal attenuation in the medium is large, is suitable for flow velocity measurement of more media, and the increased differential driving does not cause the voltage across the transducer to rapidly change, and in application, the transducer is grounded during sleep, so that the transducer is not pressurized for a long time, and the service life of the system is prevented from being reduced due to the new function.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic transducer technology, specifically to a differential driving method for ultrasonic transducers. Background Technology

[0002] With the rapid development of the Internet of Things (IoT), sensors, as core components of environmental sensing, are becoming increasingly important. Among them, ultrasonic sensors, with their advantages of low cost and relatively easy application, are widely used for short-range ranging and the measurement of gas and fluid flow rates. Ultrasonic sensing requires the use of ultrasonic transducers. During operation, the transducer at the transmitting end converts electrical signals into mechanical vibrations, thereby driving the vibration of the surrounding medium (gas or fluid) and generating ultrasonic waves. The transducer at the receiving end waits for the echo of the ultrasonic waves, and the mechanical vibrations generated by the echo are converted back into electrical signals. As long as the speed of sound in the surrounding medium is known, the propagation distance can be easily obtained by using the obtained time-of-flight (TOF) time. Furthermore, to measure the flow rate of gas or fluid, two transducers are needed to transmit and receive each other, obtaining the bidirectional TOF time between the two transducers. The time difference between these two time intervals is proportional to the flow rate of the gas or liquid in the pipe.

[0003] Figure 2 The diagram illustrates the existing distance measurement implementation structure. Two transducers have their negative terminals grounded. UT1 acts as the transmitter, and UT2 as the receiver. Fire1 transmits a positive pulse at the transducer's resonant frequency, which is then connected to the positive terminal of UT1 after passing through resistor R1. Resistor R2 at the receiver acts as the load for UT2. Upon receiving the echo, the spindle-shaped sinusoidal electrical signal is coupled to stop2 via capacitor C2 and transmitted back to the chip for processing. By timing the time from the transmission of the signal by Fire1 to the reception of the echo by Stop2, the Time-of-Flight (TOF) time can be obtained. This time, combined with the speed of sound in the medium, yields the distance between UT1 and UT2. Figure 3 The existing technical solution for measuring flow velocity is shown. The transmitter and receiver of the transducer are interchangeable. In the flow velocity measurement system, the distance between UT1 and UT2 is fixed, and the sound velocity of the medium is fixed. Therefore, the TOF time from UT1 to UT2 and the TOF time from UT2 to UT1 are only related to the flow velocity of the medium. After two TOF time measurements are performed by each other, the time difference can be converted to obtain the flow velocity of the medium.

[0004] In the flow velocity measurement of some media, due to the large attenuation of the medium, it is difficult for the system to recognize the received echo-converted electrical signal. This limits the application of the system in the flow velocity measurement of some highly attenuated media. The purpose of this invention is to increase the driving amplitude of the transducer at the transmitting end through simple modifications, thereby increasing the transducer vibration amplitude and doubling the amplitude of the received echo-converted electrical signal, thus making it suitable for the flow velocity measurement of more media. Summary of the Invention

[0005] The purpose of this invention is to differentially drive the transducer by providing negative pulses through fire1_n and fire2_n, thereby increasing the amplitude of the received electrical signal. Under conditions of low operating voltage and significant signal attenuation in the medium, a stronger electrical signal can be received, making it suitable for flow velocity measurement of more media. The increased differential drive does not cause rapid voltage changes at the transducer terminals. In application, the transducer terminals are grounded during sleep mode, preventing the transducer from being pressurized for extended periods and avoiding a decrease in system lifespan due to the added functionality.

[0006] To achieve the above effects, the present invention provides the following technical solution: a differential driving method for an ultrasonic transducer, comprising the following steps:

[0007] Step 1: Circuit Connection: Connect the circuit components. Set up six control pins on the control chip and connect each control pin to the corresponding position in the circuit.

[0008] Step 2: Use UT1 as the transmitter and UT2 as the receiver to transmit and receive ultrasonic waves.

[0009] Step 3: Use ultrasonic sensors UT1 and UT2 to measure the medium flow rate.

[0010] Step 4: Derive the impedance-matched load resistor and the signal transfer function from the transmit pin to the receive pin.

[0011] Furthermore, in step two, the circuit elements include two ultrasonic transducers UT1 and UT2, two resistors R1 and R2, and two capacitors C1 and C2.

[0012] Furthermore, in step two, the control pins are stop1, fire1, fire1_n, stop2, fire2, and fire2_n.

[0013] Furthermore, in step two, when UT1 is the transmitter and UT2 is the receiver, the Stop1 pin is in a high-impedance state, so capacitor C1 can be ignored. The fire1 and fire1_n pins are respectively given positive and negative pulses with the frequency of the transducer's resonant frequency. The fire2 and fire2_n pins on the receiver side are grounded. At this time, if the transducer UT2 and resistor R2 are impedance matched, after the transducer receives the echo with the frequency of the resonant frequency, it generates a spindle-shaped sine wave electrical signal, which is coupled to stop2 through capacitor C2 and thus received by the chip.

[0014] Furthermore, in step two, fire1 is connected to the upper plate of the transducer after passing through resistor R1, and fire1_n is directly connected to the lower plate of the transducer.

[0015] Furthermore, in step three, the step of measuring the medium flow velocity is as follows:

[0016] S301: In sleep mode, all four pins fire1, fire1_n, fire2, and fire2_n are grounded to ensure that the voltage across the transducer is 0.

[0017] S302: When UT1 transmits and UT2 receives, fire1_n is first set to 1. After all modules of the system are ready, fire1 and fire1_n transmit positive and negative pulses at the resonant frequency of the transducer, respectively. At the same time, the system starts timing and stops timing after stop2 receives the echo, and records the TOF time.

[0018] S303: After the first TOF time measurement ends, fire1_n is set to 0. Wait for a period of time to allow the ultrasonic waves in the medium to attenuate sufficiently, so as to avoid erroneous measurements in the next measurement.

[0019] S304: For the second TOF time measurement, when UT2 transmits and UT1 receives, fire2_n is first set to 1. After all modules of the system are ready, fire2 and fire2_n transmit positive and negative pulses at the resonant frequency of the transducer, respectively. At the same time, the system starts timing and stops timing after stop1 receives the echo, and records the TOF time.

[0020] S305: After completing two TOF time measurements, fire2_n is set to 0, and the system returns to sleep mode;

[0021] S306: Calculate the flow velocity of the medium.

[0022] Furthermore, in step S306, the medium flow velocity can be easily calculated by using the time difference between the two TOF times tested, the known distance between UT1 and UT2, and the known sound velocity in the medium.

[0023] Furthermore, in step four, the equivalent circuit during ranging and the equivalent circuit during transducer resonance are derived.

[0024] This invention provides a differential driving method for an ultrasonic transducer, which has the following advantages: By supplying negative pulses through fire1_n and fire2_n, the transducer is differentially driven, increasing the amplitude of the received electrical signal. Under conditions of low operating voltage and significant signal attenuation in the medium, a stronger electrical signal can be received, making it suitable for flow velocity measurement of more media. The increased differential driving does not cause rapid voltage changes at the transducer terminals. In application, the transducer terminals are grounded during sleep mode, preventing the transducer from being pressurized for extended periods and avoiding a decrease in system lifespan due to the added functionality. Attached Figure Description

[0025] Figure 1 This is a flowchart of a differential driving method for an ultrasonic transducer according to the present invention;

[0026] Figure 2 This is a distance measurement structure diagram of a prior art solution for a differential driving method for an ultrasonic transducer according to the present invention;

[0027] Figure 3 The diagram shows the flow velocity measurement structure of a prior art solution for a differential driving method for an ultrasonic transducer according to the present invention.

[0028] Figure 4 This is a structural diagram of a differential driving method for an ultrasonic transducer according to the present invention;

[0029] Figure 5 This is a distance measurement structure diagram of a differential driving method for an ultrasonic transducer according to the present invention;

[0030] Figure 6 This is a waveform diagram of the differential driving method for an ultrasonic transducer according to the present invention.

[0031] Figure 7 This is an equivalent circuit diagram for ranging in a differential driving method for an ultrasonic transducer according to the present invention.

[0032] Figure 8 This is an equivalent circuit diagram of the transducer resonance in the differential driving method of an ultrasonic transducer according to the present invention. Detailed Implementation

[0033] Please see Figure 1-8 This invention provides a technical solution: a differential driving method for an ultrasonic transducer, comprising the following steps:

[0034] Step 1: Circuit Connection: Connect the circuit components. Set up six control pins on the control chip and connect each control pin to the corresponding position in the circuit.

[0035] Step 2: Use UT1 as the transmitter and UT2 as the receiver to transmit and receive ultrasonic waves.

[0036] Step 3: Use ultrasonic sensors UT1 and UT2 to measure the medium flow rate.

[0037] Step 4: Derive the impedance-matched load resistor and the signal transfer function from the transmit pin to the receive pin.

[0038] Specifically, in step two, the circuit components include two ultrasonic transducers UT1 and UT2, two resistors R1 and R2, and two capacitors C1 and C2. The two ultrasonic transducers are used to transmit or receive ultrasonic waves. In one speed measurement process, UT1 is used as the transmitter and UT2 as the receiver to perform a TOF time measurement. Then, the state is switched so that UT2 is used as the transmitter and UT1 as the receiver to perform another TOF time measurement. Since the distance is fixed and the sound velocity in the medium is the same, the TOF time difference is only proportional to the flow velocity of the medium. The two resistors R1 and R2 are mainly used to match the impedance of the transducer at the resonant frequency, so that the system can achieve the optimal energy transfer efficiency, thereby generating a large swing during reception. At the same time, at the transmitter, the resistors act as filters to prevent the voltage at the positive and negative ends of the transducer from changing too quickly. This helps to avoid a rapid decline in the lifespan of the transducer. The two capacitors are used to couple the electrical signal generated by the transducer to stop1 or stop2 and transmit it back to the chip. At the transmitter, the other end of the capacitor, stop1 or stop2, is in a high-impedance state, so the capacitor does not affect the behavior of the transmitter.

[0039] Specifically, in step two, the control pins are stop1, fire1, fire1_n, stop2, fire2, and fire2_n.

[0040] Specifically, in step two, when UT1 acts as the transmitter and UT2 as the receiver, the Stop1 pin is in a high-impedance state, so capacitor C1 can be ignored. The fire1 and fire1_n pins are respectively supplied with positive and negative pulses at the transducer's resonant frequency. The fire2 and fire2_n pins on the receiver side are grounded. If the transducer UT2 and resistor R2 are impedance matched, the transducer, upon receiving the echo at its resonant frequency, generates a spindle-shaped sine wave electrical signal. This signal is coupled to stop2 through capacitor C2 and thus received by the chip. By adding the fire1_n and fire2_n pins, the inverted pulses supplied to fire1 and fire2 during transmission increase the transducer's vibration amplitude, thereby strengthening the electrical signal generated by the echo. The signal received by stop1 or stop2... The electrical signal amplitude is doubled, allowing for the reception of stronger electrical signals even at lower operating voltages and with greater signal attenuation in the medium. This makes it suitable for flow rate measurement in a wider range of media. The Fire1 and Fire2 pins are connected to the positive terminal of the transducer via a resistor. The resistor and the internal capacitor of the transducer form a filter. Even with the addition of Fire1_n and Fire2_n pins to provide negative pulses, the filter remains, and the voltage across the ultrasonic transducer will not change rapidly. This avoids the reduction in lifespan caused by rapid voltage changes across the transducer, making it more suitable for applications requiring ultra-long-term operation. During the sleep phase, all four pins—Fire1, Fire1_n, Fire2, and Fire2_n—are grounded to ensure that the voltage across the transducer is 0 most of the time, preventing a reduction in lifespan caused by prolonged voltage application.

[0041] Specifically, in step two, fire1 is connected to the upper plate of the transducer after passing through resistor R1, and fire1_n is directly connected to the lower plate of the transducer.

[0042] Specifically, in step three, the steps for measuring the medium flow velocity are as follows:

[0043] S301: In sleep mode, all four pins fire1, fire1_n, fire2, and fire2_n are grounded to ensure that the voltage across the transducer is 0.

[0044] S302: When UT1 transmits and UT2 receives, fire1_n is first set to 1. After all modules of the system are ready, fire1 and fire1_n transmit positive and negative pulses at the resonant frequency of the transducer, respectively. At the same time, the system starts timing and stops timing after stop2 receives the echo, and records the TOF time.

[0045] S303: After the first TOF time measurement ends, fire1_n is set to 0. Wait for a period of time to allow the ultrasonic waves in the medium to attenuate sufficiently, so as to avoid erroneous measurements in the next measurement.

[0046] S304: For the second TOF time measurement, when UT2 transmits and UT1 receives, fire2_n is first set to 1. After all modules of the system are ready, fire2 and fire2_n transmit positive and negative pulses at the resonant frequency of the transducer, respectively. At the same time, the system starts timing and stops timing after stop1 receives the echo, and records the TOF time.

[0047] S305: After completing two TOF time measurements, fire2_n is set to 0, and the system returns to sleep mode;

[0048] S306: Calculate the flow velocity of the medium.

[0049] Specifically, in step S306, the medium flow velocity can be easily calculated by using the time difference between the two TOF times tested, the known distance between UT1 and UT2, and the known sound velocity in the medium.

[0050] Specifically, in step four, the equivalent circuit during ranging and the equivalent circuit during transducer resonance are derived.

[0051] The derivation process of the load resistance for impedance matching is as follows:

[0052] like Figure 7 As shown, transducer UT1 can be equivalent to a static capacitor C. e0 A parallel connection with a series path, the series path being composed of resistor R. e1 Capacitor C e1 and inductor L e1 Similarly, the transducer UT2 can be considered equivalent to a static capacitor C. e3 A parallel connection with a series path, the series path being composed of resistor R. e2 Capacitor C e2 and inductor L e2 In application, transducers UT1 and UT2 are identical in model, therefore the resistance, capacitance, and inductance values ​​of the equivalent model are equal.

[0053]

[0054] When the input frequency satisfies the formula above, it is equal to the resonant frequency f. z At this time, the effects of inductance and capacitance in the series circuit of the transducer will cancel each other out.

[0055] like Figure 8 As shown, when the transducer resonates, the impedance Z of the transducer is... UT1 For resistor R e1 and capacitor C e0 The parallel connection is shown in the formula.

[0056]

[0057] After derivation, the impedance Z UT1 It can be transformed into the form R+jX, as shown in the formula below, where the real part represents the resistance and the imaginary part represents the reactance.

[0058]

[0059] Since this scheme uses resistors for impedance matching, the imaginary part is ignored, and the load resistance should be equal to the impedance Z. UT1 The real part of is shown in the formula below.

[0060]

[0061] Next, regarding V... fire1 To V stop2 The transfer function is derived as follows:

[0062]

[0063] V fire1 Converted into electrical power P on transducer UT1 t As shown in the formula above.

[0064] P t =P s T s

[0065] The above formula shows the transmitted electrical power P s Converted into transmitted sound power P t T s The sound-to-electric conversion efficiency at the transmitting end.

[0066] P r =P t L = P t e -αd

[0067] Where P r Let L be the acoustic power at the receiver, L be the attenuation coefficient of the medium, α be the attenuation constant of the medium, and d be the distance from the transmitter to the receiver.

[0068] P e =P r T r

[0069] Received sound power P r Converted into received electrical power P e T r The sound-to-electric conversion efficiency at the receiving end.

[0070]

[0071] The open-loop voltage of the transducer is shown in the formula above.

[0072]

[0073] When C2 is large enough and the stop2 pin has high impedance, V can be considered... stop2 The voltage drop across the load resistor R2 is equal to the voltage across the load resistor R2. Then, V can be obtained using the voltage divider formula. stop2 .

[0074] Combining the above formula, we can obtain

[0075]

[0076] When R1 = R2, Z UT1 =Z UT2 At that time, it can be simplified to

[0077]

[0078] According to the formula above, since T s T r α and Z UT1 These are all determined by physical characteristics, such as distance d and driving voltage V. fire1 With R1 remaining constant, the closer it is to Z UT1 V stop2 The stronger the signal, the more we can set R1 equal to Z since R1 has no imaginary part. UT1 The real part of the tampere can be used to achieve impedance matching, which can maximize transmission efficiency.

[0079] At the same time, according to the above formula, it can be seen that through differential driving, V fire1 Doubling the signal can bring V stop2 The signal doubled.

[0080] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A differential driving method for an ultrasonic transducer, characterized in that, Includes the following steps: S1. Circuit Connection: Connect the circuit components. Six control pins, stop1, fire1, fire1_n, stop2, fire2, and fire2_n, are set on the control chip. Connect each control pin to its corresponding position in the circuit. The circuit components include two ultrasonic transducers UT1 and UT2, two resistors R1 and R2, and two capacitors C1 and C2. Specifically, fire1 is connected to the upper plate of transducer UT1 via resistor R1, and fire1_n is directly connected to the lower plate of transducer UT1. Similarly, fire2 is connected to the upper plate of transducer UT2 via resistor R2, and fire2_n is directly connected to the lower plate of transducer UT2. S2. Using UT1 as the transmitter and UT2 as the receiver to transmit and receive ultrasonic waves; when UT1 is the transmitter and UT2 is the receiver, the stop1 pin is in a high-impedance state, the fire1 and fire1_n pins are respectively given a positive pulse and a negative pulse with a frequency of the transducer resonant frequency, and the fire2 and fire2_n pins are grounded; after receiving the echo with a frequency of the resonant frequency, the transducer UT2 generates an electrical signal, which is coupled to stop2 through capacitor C2; S3. Use ultrasonic transducers UT1 and UT2 to measure the medium flow velocity. In sleep mode, all four pins fire1, fire1_n, fire2, and fire2_n are grounded. When UT1 transmits and UT2 receives, fire1_n is first set to 1, then fire1 and fire1_n transmit positive and negative pulses respectively, and the first TOF time is recorded. After the first measurement, fire1_n is set to 0, and the system waits for the ultrasonic waves to attenuate in the medium. When UT2 transmits and UT1 receives, fire2_n is first set to 1, then fire2 and fire2_n transmit positive and negative pulses respectively, and the second TOF time is recorded. After completing the two measurements, fire2_n is set to 0, and the system returns to sleep mode. Calculate the medium flow velocity based on the time difference between the two TOF times. S4. Derive the load resistance for impedance matching and the transmission function of the signal from the transmit pin to the receive pin: Based on the equivalent circuit during ranging and the equivalent circuit during transducer resonance, derive the load resistances R1 and R2 to be equal to the real part of the impedance during transducer resonance to achieve impedance matching.

2. The differential driving method for an ultrasonic transducer according to claim 1, characterized in that: In step S2, the fire1 and fire2 pins are connected to the positive terminal of the transducer through a resistor. The resistor and the internal capacitor of the transducer form a filter to prevent rapid voltage changes across the transducer.

3. The differential driving method for an ultrasonic transducer according to claim 1, characterized in that: In step S3, the medium flow velocity is calculated by using the time difference between the two TOF times, the known distance between UT1 and UT2, and the known sound velocity in the medium.

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