Design method for impedance matching circuit of transducer based on large signal

Abstract

The invention discloses a transducer impedance matching circuit design method based on a large signal. The method mainly comprises the following steps: determining a working frequency band of a transducer; selecting an impedance test frequency point in the working frequency band; measuring the voltage and current of the transducer under the working voltage level; the transducer impedance is calculated through the voltage and current waveforms; selecting a matching frequency point in the working frequency band; and designing a matching circuit according to impedance characteristics of the transducer, and calculating matching parameters and the like. According to the method, the impedance characteristic is tested by using a large voltage signal and is closer to the impedance characteristic during working, and the matching circuit designed according to the impedance characteristic has a better matching effect during working, so that the output active power of the power amplifier is improved, and the output sound field intensity of the transducer is improved.

Description

Technical Field

[0001] The invention relates to the technical field of impedance matching, and in particular to a design method for a transducer impedance matching circuit based on a large signal. Background Art

[0002] Piezoelectric transducer is a kind of underwater acoustic load that generates sound by vibrating ceramic plates through high voltage. It is widely used in detection, military and other fields. Since piezoelectric transducer is a resistive-capacitive load for power amplifier, and its voltage emission response and impedance characteristics vary with frequency, in high-power sound radiation system, the impedance of transducer is usually matched by designing a suitable matching circuit, so that the overall load after matching is as pure as possible for the power amplifier, thereby improving the active power output of the power amplifier and increasing the output sound field intensity of the transducer.

[0003] The existing matching circuit design method is usually divided into the following steps. First, use an impedance analyzer or other equipment to test the equivalent impedance of the required matching transducer at each frequency point in the working frequency band. Then select the corresponding matching frequency point based on the equivalent impedance and voltage emission response measured by the transducer. Then design the matching circuit based on the tested transducer impedance and the selected matching frequency point and calculate the matching inductance and capacitance parameters.

[0004] In the above method, an impedance analyzer is usually used to test the impedance of the transducer. The impedance analyzer tests the impedance by outputting a sinusoidal voltage signal not exceeding 10V to the transducer and measuring the current signal input to the transducer at the same time, thereby calculating the equivalent impedance data of the transducer. However, for piezoelectric transducers, under large voltage excitation, they will present impedance characteristics that are completely different from those under small signals. Therefore, if the impedance characteristics measured by small signals are used to design the matching circuit, it will lead to problems such as unreasonable matching circuit design and poor matching effect. Summary of the invention

[0005] The present disclosure provides a large-signal-based transducer impedance matching circuit design method, which uses a large voltage signal instead of a small-signal-measured transducer impedance to design a matching circuit, thereby achieving a better matching effect.

[0006] The present disclosure provides a large signal based transducer impedance matching circuit design method, comprising the following steps:

[0007] S1, determine the working frequency band of the transducer;

[0008] S2, select the impedance test frequency point within the working frequency band;

[0009] S3, connecting the output terminal of the power amplifier to the transducer, and measuring the voltage and current of the transducer at the working voltage level;

[0010] S4, calculating the equivalent impedance of the transducer at each frequency point according to the voltage and current waveforms;

[0011] S5, selecting a suitable matching frequency point according to the calculated transducer equivalent impedance and transmission voltage response;

[0012] S6, designing a matching circuit according to the impedance characteristics of the transducer and calculating matching parameters.

[0013] Furthermore, in step S2,

[0014] The selected test frequency points should be evenly distributed within the operating frequency band and as densely as possible.

[0015] Furthermore, the step S3 specifically includes:

[0016] Connect the output end of the power amplifier to the transducer, turn on the power amplifier, output a sinusoidal signal of the selected frequency to the transducer, and slowly increase the output voltage until it reaches the operating voltage level;

[0017] Use an oscilloscope to measure the voltage and current waveforms at this voltage level and export the data.

[0018] Furthermore, the specific method of step S4 includes:

[0019] Assuming that the collected voltage and current waveforms are sinusoidal waves, read the voltage amplitude U, current amplitude I, period T, and voltage and current phase difference in the data. And the voltage and current expressions can be obtained as follows:

[0020] u=Usin(ωt)

[0021]

[0022] in,

[0023] The piezoelectric transducer is a resistive-capacitive load, which can be equivalent to a resistor and a capacitor in parallel. Let Rp be the equivalent parallel resistor and Cp be the equivalent parallel capacitor.

[0024] The voltage applied to the capacitor and resistor is u, then the current flowing through the resistor and capacitor is calculated as follows:

[0025]

[0026] The total current is the sum of the two currents:

[0027]

[0028] at the same time,

[0029]

[0030] Combining the above two equations, we can get:

[0031]

[0032] By using the above formula, the equivalent impedance of the transducer is calculated at each tested frequency point.

[0033] Furthermore, in step S5, the principle of selecting the matching frequency point includes: the impedance in the frequency band near the frequency point is relatively stable, and the voltage emission response is relatively low at the frequency point.

[0034] Furthermore, the specific method of step S6 includes:

[0035] For single frequency point matching method: Since the transducer is a resistive-capacitive load, a single inductor series matching method is adopted for a single frequency point, where Ls is the series matching inductor.

[0036]

[0037] The series inductance Ls is calculated as follows:

[0038]

[0039] Among them, f is the frequency point selected for matching.

[0040] Furthermore, in step S5, if the working frequency band has a wide bandwidth, multiple frequency points are selected for matching.

[0041] Furthermore, the method further comprises the following steps:

[0042] Prepare a kW-class power amplifier with controllable output, an oscilloscope, a high-voltage probe, and a current probe. The oscilloscope is used to obtain the voltage and current waveforms at the operating voltage level.

[0043] Compared with the prior art, the beneficial effects of the present invention are: (1) the impedance characteristics are tested with a large voltage signal, which is closer to the impedance characteristics during operation. The matching circuit designed according to this impedance characteristic will have a better matching effect during operation; (2) the active power output of the power amplifier is increased, and the intensity of the sound field output by the transducer is increased; (3) the method is simple and feasible; and (4) it has good versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present disclosure.

[0045] Figure 1is a flow chart of an exemplary embodiment according to the present disclosure;

[0046] Figure 2 is an exemplary voltage and current waveform diagram of a transducer;

[0047] Figure 3 is the equivalent RC parallel circuit of the transducer;

[0048] Figure 4 The equivalent circuit of the transducer series connection. DETAILED DESCRIPTION

[0049] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0050] Since the piezoelectric transducer exhibits completely different impedance characteristics when excited by a large voltage compared with a small signal; if the impedance characteristics measured by a small signal are used to design a matching circuit, the impedance characteristics change when the transducer is working, which will cause the matching circuit to fail to achieve the best matching effect. Therefore, the present disclosure provides a transducer impedance matching circuit design method based on a large signal. In an exemplary embodiment, as shown in the attached Figure 1 As shown, it mainly includes the following steps:

[0051] 1. First, you need to prepare a kW-class power amplifier with controllable output, an oscilloscope, a high-voltage probe, and a current probe;

[0052] 2. Determine the working frequency band of the transducer and reasonably select the test frequency points. The selected test frequency points should be evenly distributed within the working frequency band and as dense as possible;

[0053] 3. Connect the output end of the power amplifier to the transducer, turn on the power amplifier, output a sinusoidal signal of the selected frequency to the transducer, and slowly increase the output voltage until it reaches the operating voltage level;

[0054] 4. Use an oscilloscope to measure the voltage and current waveforms at this voltage level and export the data;

[0055] 5. Then calculate the equivalent impedance of the transducer at each frequency point based on the measured voltage and current waveforms:

[0056] Assume that the collected voltage and current waveforms are as shown in the attached Figure 2 As shown, the voltage amplitude U, current amplitude I, period T and voltage and current phase difference can be read from the data. And the voltage and current expressions can be obtained as follows:

[0057] u=Usin(ωt)

[0058]

[0059] in,

[0060] The piezoelectric transducer is a resistive-capacitive load, which can be equivalent to a resistor and a capacitor in parallel. The equivalent circuit is shown in the attached figure. Figure 3 As shown in the figure, Rp is the equivalent parallel resistance and Cp is the equivalent parallel capacitance.

[0061] The voltage applied to the capacitor and the resistor is u, so the current flowing through the resistor and the capacitor can be calculated as follows:

[0062]

[0063] The total current is the sum of the two currents:

[0064]

[0065] at the same time,

[0066]

[0067] Combining the above two equations, we can get:

[0068]

[0069] By using the above formula, the equivalent impedance of the transducer is calculated at each tested frequency point.

[0070] 6. Select a suitable matching frequency point based on the calculated equivalent impedance of the transducer and the emission voltage response. The selection principles include: the impedance in the frequency band near this frequency point is relatively stable; the voltage emission response at this frequency point is relatively low, etc.

[0071] If the working frequency band is wide, multiple frequency points can also be selected for matching.

[0072] 7. Design the matching circuit according to the transducer impedance characteristics and calculate the matching parameters:

[0073] In this embodiment, single frequency matching is taken as an example. Since the transducer is a resistive-capacitive load, a single inductor series matching method is adopted for a single frequency point. At this time, the matching circuit and the equivalent circuit are shown in the attached figure. Figure 4 shown.

[0074] Wherein, Ls is the series matching inductor.

[0075]

[0076] The series inductance Ls is calculated as follows:

[0077]

[0078] Among them, f is the frequency point selected for matching.

[0079] The above technical scheme is only an exemplary embodiment of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific embodiment of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

Claims

1. A method for designing a transducer impedance matching circuit based on a large signal, comprising the following steps: S1, determine the working frequency band of the transducer; S2, select the impedance test frequency point within the working frequency band; S3, connecting the output terminal of the power amplifier to the transducer, and measuring the voltage and current of the transducer at the working voltage level; S4, calculating the equivalent impedance of the transducer at each frequency point according to the voltage and current waveforms; S5, selecting a suitable matching frequency point according to the calculated transducer equivalent impedance and transmission voltage response; S6, designing a matching circuit according to the impedance characteristics of the transducer and calculating matching parameters.

2. The method according to claim 1, characterized in that In the step S2, The selected test frequency points should be evenly distributed within the operating frequency band and as densely as possible.

3. The method according to claim 1, characterized in that The step S3 specifically includes: Connect the output end of the power amplifier to the transducer, turn on the power amplifier, output a sinusoidal signal of the selected frequency to the transducer, and slowly increase the output voltage until it reaches the operating voltage level; Use an oscilloscope to measure the voltage and current waveforms at this voltage level and export the data.

4. The method according to claim 1, characterized in that: The specific method of step S4 includes: Assuming that the collected voltage and current waveforms are sinusoidal waves, read the voltage amplitude U, current amplitude I, period T, and voltage and current phase difference in the data. And the voltage and current expressions can be obtained as follows: u=Usin(ωt) in, The piezoelectric transducer is a resistive-capacitive load, which can be equivalent to a resistor and a capacitor in parallel. Let Rp be the equivalent parallel resistor and Cp be the equivalent parallel capacitor. The voltage applied to the capacitor and resistor is u, then the current flowing through the resistor and capacitor is calculated as follows: The total current is the sum of the two currents: at the same time, Combining the above two equations, we can get: By using the above formula, the equivalent impedance of the transducer is calculated at each tested frequency point.

5. The method according to claim 1, characterized in that: In step S5, the principles for selecting the matching frequency point include: the impedance in the frequency band near the frequency point is relatively stable, and the voltage emission response is relatively low at the frequency point.

6. The method according to claim 4, characterized in that The specific method of step S6 includes: For single frequency point matching method: Since the transducer is a resistive-capacitive load, a single inductor series matching method is adopted for a single frequency point, where Ls is the series matching inductor. The series inductance Ls is calculated as follows: Among them, f is the frequency point selected for matching.

7. The method according to claim 5, characterized in that In step S5, if the working frequency band has a wide bandwidth, multiple frequency points are selected for matching.

8. The method according to any one of claims 1 to 7, further comprising the following steps: Prepare a kW-class power amplifier with controllable output, an oscilloscope, a high-voltage probe, and a current probe. The oscilloscope is used to obtain the voltage and current waveforms at the operating voltage level.

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