CN102291656B - Static matching fast debugging method for power ultrasonic transducer - Google Patents

Abstract

The invention discloses a fast debugging method for static matching of a power ultrasonic transducer. Power source excitation, the debugging method is to divide the tuning and filtering into two steps to debug separately. A fast debugging method for static matching of a power ultrasonic transducer according to the present invention, the filtering and tuning are debugged step by step, used for static matching of the transducer, the matching effect is good, and the static capacitance and dynamic resistance of the transducer can be measured at the same time , the measurement equipment is simple, easy to implement, and has high measurement accuracy.

Description

A Quick Debugging Method for Static Matching of Power Ultrasonic Transducers

technical field

The invention relates to a static matching debugging method of a power ultrasonic transducer, belonging to the technical field of power ultrasonic matching.

Background technique

Matching is an important part of power ultrasound technology. Static matching is the matching between the output impedance of the power source and the static input impedance of the transducer under the condition that the output frequency of the ultrasonic power source is the same as the static resonance frequency of the transducer. It is suitable for applications requiring a fixed output frequency of the transducer.

According to Qin Wen pointed out in the document "High Power Sine Wave Ultrasonic Power Supply": "Ultrasonic application manufacturers and Tianxing Rare Earth Company have conducted experiments on ultrasonic transducers using rare earth giant magnetostrictive materials as probes. The experimental data show that using square wave Or the efficiency of the ultrasonic transducer is low when the pulse power supply is used, and the use of sine wave excitation can greatly improve the ultrasonic efficiency." The common ultrasonic power source generally adopts an inverter structure, and its output is a square wave. In order to effectively drive the transducer, the static matching circuit should have a filtering function in addition to tuning. Common matching methods include parallel inductance, series inductance, inductance and capacitance (LC), improved inductance and capacitance (LCC), and T-type matching methods. The shunt inductor method is less used now due to poor filtering performance. Several other methods design and debug the filter tuning as a whole, the theoretical derivation is relatively complicated, and the circuit debugging is difficult.

Contents of the invention

The technical problem to be solved by the present invention is to provide a fast debugging method for static matching of power ultrasonic transducers, which is used for static matching of transducers. At the same time, the static capacitance and dynamic resistance of the transducer can be measured. The measuring device is simple, easy to implement, and has high measurement accuracy.

In order to solve the above technical problems, the present invention provides a step-by-step debugging method based on filter tuning, which is carried out through a step-by-step debugging method according to function, and also provides a method for measuring the static capacitance and dynamic resistance of the transducer.

The present invention divides the static matching into two relatively independent parts of filtering and tuning for debugging. The principle is: for an ultrasonic power source whose output is a square wave, whether it is LC, LCC or T-type static matching circuit, the main functions of the circuit can be divided into two parts: one is to filter the output of the ultrasonic power source to obtain the driving The sinusoidal signal required by the transducer; the second is to tune the transducer so that the impedance of the entire circuit is purely resistive. Starting from these two functional requirements, the completion of filtering and tuning is the completion of static matching.

A power ultrasonic transducer static matching fast debugging method is characterized in that, in the debugging circuit, the power ultrasonic transducer is connected in series with a filter capacitor, a filter inductor, a tuning inductor, and a load resistor, and the power ultrasonic transducer is excited by an ultrasonic power source, The debugging method is to divide the tuning and filtering into two steps to debug separately:

Step 1: Use sine wave excitation to drive the power ultrasonic transducer, tune and debug the power ultrasonic transducer, measure various data at resonance, and obtain the equivalent resistance, equivalent capacitance, Dynamic resistance, static capacitance;

Step 2: The load resistance value is taken as the equivalent resistance value when the power ultrasonic transducer resonates, and the ultrasonic power source is filtered and debugged by adjusting the tuning inductance, and the filter capacitor and filter inductance are measured and obtained;

Step 3: Perform integrated debugging of tuning and filtering for the power ultrasonic transducer, adjust the tuning inductance, and complete static matching when the phase of the waveform on the load resistor is the same as that in the debugging circuit.

The ultrasonic power source is a high-power ultrasonic power source.

The load resistor is a high-power resistor.

The load resistor is a non-inductive resistor.

A transformer is provided between the ultrasonic power source and the power ultrasonic transducer.

A signal acquisition device is used for measurement, and the signal acquisition device collects and reads voltage and current signals.

The signal acquisition device includes an oscilloscope.

The beneficial effects achieved by the present invention: a fast debugging method for static matching of power ultrasonic transducers in the present invention, the filtering and tuning are debugged step by step, used for static matching of transducers, the matching effect is good, and can be measured at the same time Transducer static capacitance, dynamic resistance, the measurement equipment is simple, easy to implement, and has high measurement accuracy.

Description of drawings

Figure 1 Schematic diagram of static matching debugging device;

The schematic diagram of the equivalent circuit of the transducer in Fig. 2a;

The schematic diagram of the equivalent circuit of the transducer at the resonance point in Fig. 2b;

Fig. 2c is a schematic diagram of the equivalent series circuit of Fig. 2b;

Fig. 3 schematic diagram of transducer tuning circuit;

Fig. 4 transducer filter circuit schematic diagram;

Figure 5 is a schematic diagram of the overall debugging of the tuning filter.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings. The following examples are only used to illustrate the technical solution of the present invention more clearly, but not to limit the protection scope of the present invention.

Example 1

The static matching debugging device is shown in Figure 1. It mainly includes an ultrasonic transducer Z for realizing acoustic-electric conversion (hereinafter referred to as transducer Z), and a self-made ultrasonic power source for driving transducer Z. The self-made transmission line transformer T is connected between the two main parts for isolation and impedance transformation. The signal acquisition devices are oscilloscopes 1 and 2 to collect and read voltage and current signals.

The debugging method is as follows:

The requirement of tuning function can be realized by series inductance; the design of filtering part can be realized by L and C series resonance. The specific circuit is shown in Figure 1. Among them, the function of inductor L _p and capacitor C _p is filtering (that is, frequency selection), the function of inductor _L1 is tuning (that is, phase compensation), and resistor R1 is a load resistor connected in series with the power ultrasonic transducer. The equivalent circuit of the transducer Z is shown in Figure 2a, where the capacitance _C0 is the static capacitance of the transducer, the inductance L is the dynamic inductance of the transducer, the capacitance C is the dynamic capacitance of the transducer, and the resistance R is the dynamic resistance of the transducer. The circuit at the resonance point can be equivalent to Figure 2b, and its equivalent series circuit is shown in Figure 2c, the resistance R _e is the series equivalent resistance of the transducer Z, and the capacitance C _e is the equivalent capacitance.

(1) Tuning part

Use the signal source to connect according to Figure 3, where R ₁ is the sampling resistor. Adjust the inductance L ₁ so that the waveforms of oscilloscope 1 and oscilloscope 2 are in phase, that is, tuning. Note that the waveform voltage peak value of oscilloscope 1 is u ₁ , the waveform voltage peak value of oscilloscope 2 is u ₂ , and the angular frequency of the voltage waveform is ω _s . Inductance value L ₁ .

According to the principle of voltage division of the circuit, it can be obtained:

$R_e=\frac{u_1-u_2}{u_2}{R}_1$ Formula 1)

因此，可得：When the circuit resonates,

Therefore, we can get:

$C_e=\frac{1}{{{\mathrm{\ω}}_{\mathrm{the\; s}}}^2{L}_1}$ Formula (2)

The parallel connection of resistors and capacitors (Fig. 2b) is equivalent to the series connection of resistors and capacitors (Fig. 2c). According to the circuit equivalent principle, we can get:

$R_e=\frac{R}{1+{\left({\mathrm{\ω}}_{\mathrm{the\; s}}{C}_{0}R\right)}^2}$ Formula (3)

$C_e=\frac{C_0}{{\left({\mathrm{\ω}}_{\mathrm{the\; s}}{C}_{0}R\right)}^2}(1+{\left({\mathrm{\ω}}_{\mathrm{the\; s}}{C}_{0}R\right)}^2)$ Formula (4)

Re _and C _e are calculated from formula (1) and formula (2).

By multiplying formula (3) and formula (4), the following formula can be obtained,

${\mathrm{\ω}}_{\mathrm{the\; s}}{C}_{0}R=\frac{1}{{\mathrm{\ω}}_{\mathrm{the\; s}}{C}_e{R}_e}$ Formula (5)

Substituting Equation (5) into Equation (3) and Equation (4), the dynamic resistance R and the static capacitance C ₀ of the transducer can be calculated, as shown in Equation (6) and Equation (7) below,

$R=R_e(1+\frac{1}{{\left({\mathrm{\ω}}_{\mathrm{the\; s}}{C}_e{R}_e\right)}^2})$ Formula (6)

$C_0=\frac{C_e}{1+{\left({\mathrm{\ω}}_{\mathrm{the\; s}}{C}_e{R}_e\right)}^2}$ Formula (7)

(2) Filtering part

根据式(8)、式(9)计算电感L_p、电容C_p的值。Filter part parameter calculation, at the series resonance point f _s , select the appropriate loop quality factor Q value, Q is defined by the ratio of the loop resonance resistance to the characteristic impedance,

Calculate the values of inductance L _p and capacitance C _p according to formula (8) and formula (9).

$L_p=\frac{Q}{{\mathrm{\&omega;}}_{\mathrm{the\; s}}}{R}_e=\frac{Q}{{\mathrm{\&omega;}}_{\mathrm{the\; s}}}\frac{R}{1+{{\mathrm{\&omega;}}_{\mathrm{the\; s}}}^2{C_0}^2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="110402111658.png,110402111744.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}$ Formula (8)

$C_p=\frac{1}{{\mathrm{\&omega;}}_{\mathrm{the\; s}}Q{R}_e}=\frac{1+{{\mathrm{\&omega;}}_{\mathrm{the\; s}}}^2{C_0}^2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="110402111658.png,110402111744.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}{{\mathrm{\&omega;}}_{\mathrm{the\; s}}\mathrm{QR}}$ Formula (9)

Example 2

In this embodiment, on the basis of implementation 1, the resonant frequency of the transducer Z is selected as f _s =290.739kHz, and the detailed calculation of the debugging process is performed.

The debugging process is:

(1) Tuning part

Tuning part of the design, the specific debugging circuit shown in Figure 3. Wind the inductance L ₁ by yourself, adjust the inductance L ₁ , when the phases of the waveforms of the two channels are the same, the tuning is realized. The measured inductance L ₁ =0.026mH, u ₁ =16.24V, u ₂ =8.06V, through calculation, _Re =100Ω, C _e =11.52nF, R=122.58Ω, C ₀ =2.12nF.

(2) Filtering part

The design of the filtering part, the specific debugging circuit is shown in Figure 4. The value of the resistance R ₁ is equal to or close to the value of the series equivalent resistance _Re of the transducer Z. Calculated according to formula (1), R _e ≈100Ω. The selection of Q value should be moderate; in addition, the common value of capacitance should be taken into consideration. Assuming that the selected Q value is 6, the capacitance C _p calculated by formula (9) is 0.912nF. Considering the common values of capacitors, finally choose the capacitor C _p =1nF, then Q≈5.474, and the inductance L _p ≈0.300mH. Wind the inductance by yourself according to the calculation results, adjust the inductance value, and when the oscilloscope 2 shows an ideal sine wave (at this time, the inductance and capacitance also resonate, and the two oscilloscopes display the same phase of the waveform), the filtering function is realized. The actual capacitance C _p is 1nF, and the resistance R ₁ is 100Ω. The actual inductance _Lp value is measured as 0.303mH, which is close to the theoretical value.

The problems _that need to be paid attention to during the debugging process are: (1) Because the output power of the ultrasonic power source is relatively large, the resistor _R1 should be a high-power resistor; Non-inductive resistors are preferred. (2) In order to conform to the actual high-power operating environment, in this embodiment, a self-made ultrasonic power source is selected instead of a common signal source, and a transformer T required in actual use is connected between the filter circuit and the power source. (3) When the circuit is working, the voltage across the capacitor will be Q times the voltage across the Z equivalent resistance of the transducer. Considering that the capacitor has a certain withstand voltage limit, the Q value is not easy to choose too large; and considering the commonly used capacitor value. Considering comprehensively in this embodiment, the Q value is 5.474, and the capacitance is 1nF. In other embodiments, it needs to be selected according to specific circuit parameters. Secondly, due to heat generation, the capacitance value of the capacitor will change, which will cause the resonance point to drift. Therefore, a capacitor with high withstand voltage and small temperature drift should be selected. (4) The leakage inductance of the transformer should be small to avoid peak voltage at the moment the power tube is turned off, which is not good for the circuit work, and may even burn the power tube in severe cases.

(3) Overall debugging

Combining the tuning part and the filtering part for overall debugging, the circuit diagram is shown in Figure 5. Keep the filter inductance L _p unchanged, adjust the inductance L ₁ , when the two oscilloscopes display the same waveform phase, the filtering and tuning are realized, and the static matching function is completed. Finally, the inductance L ₁ is determined to be 0.030mH.

Through the above divisional debugging methods, the results show that the theoretical calculation and the measured data are in good agreement. And the calculation is relatively simplified compared with the overall debugging, and the debugging is also more convenient.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and modifications can also be made. It should also be regarded as the protection scope of the present invention.

Claims (7)

1. A fast debugging method for static matching of a power ultrasonic transducer, characterized in that the debugging circuit includes a power ultrasonic transducer, a filter capacitor, a filter inductor, a tuning inductor, and a load resistor, and the power ultrasonic transducer is composed of an ultrasonic power source Excitation, the debugging method is to divide the tuning and filtering into two steps to debug separately: Step 1: Connect the power ultrasonic transducer in series with the tuning inductance and load resistance, use sine wave excitation to drive the power ultrasonic transducer, tune and debug the power ultrasonic transducer, measure various data at resonance, and obtain by calculation Equivalent resistance, equivalent capacitance, dynamic resistance, and static capacitance of power ultrasonic transducers; Step 2: Connect the filter capacitor, filter inductance, and load resistance in series, and the load resistance value is the equivalent resistance value when the power ultrasonic transducer resonates. By adjusting the filter inductance, filter and debug the ultrasonic power source, measure and obtain Filter capacitor, filter inductance value; Step 3: Connect the power ultrasonic transducer in series with the filter capacitor, filter inductance, tuning inductance, and load resistance, and perform integrated debugging for tuning and filtering of the power ultrasonic transducer, and adjust the tuning inductance. When the phase of the waveform on the load resistance and the debugging circuit Static matching is done when the phases of the waveforms in are the same. 2. A fast debugging method for static matching of a power ultrasonic transducer according to claim 1, wherein the ultrasonic power source is a high-power ultrasonic power source. 3. A fast debugging method for static matching of a power ultrasonic transducer according to claim 1, wherein the load resistor is a high-power resistor. 4. A fast debugging method for static matching of a power ultrasonic transducer according to claim 1, wherein the load resistor is a non-inductive resistor. 5 . The method for statically matching and quick debugging of a power ultrasonic transducer according to claim 1 , wherein a transformer is provided between the ultrasonic power source and the power ultrasonic transducer. 6 . 6. A fast debugging method for static matching of a power ultrasonic transducer according to claim 1, characterized in that a signal acquisition device is used during measurement. 7. A fast debugging method for static matching of a power ultrasonic transducer according to claim 6, wherein the signal acquisition device includes an oscilloscope.

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