Impedance matching circuit for detecting dynamic branch current of megasonic transducer

Abstract

The invention provides an impedance matching circuit for detecting the dynamic branch current of a megasonic transducer, and the method comprises the steps: constructing an impedance matching circuit for detecting the dynamic branch current of the megasonic transducer, and the impedance matching circuit comprises a half-bridge drive circuit, an LC impedance matching network and a megasonic transducer equivalent circuit model; the megasonic transducer equivalent circuit model is connected with the LC impedance matching circuit to form a Huygens bridge for extracting a dynamic branch current equivalent feedback voltage; the half-bridge driving circuit is used for converting a direct-current input voltage into an alternating-current high-voltage square wave driving signal; the LC impedance matching network is used for realizing the effects of impedance conversion, tuning and filtering; according to the megasonic transducer, the effects of impedance conversion, tuning and filtering are achieved in a wide load range, and the energy conversion efficiency of the megasonic transducer is improved.

Description

Technical Field

[0001] This invention belongs to the field of transducer matching technology, specifically relating to an impedance matching circuit for detecting the dynamic branch current of a megasonic transducer. Background Technology

[0002] The megohmmeter transducer is the core component of the megohmmeter cleaning machine. It uses the inverse piezoelectric effect to convert electrical energy into high-frequency mechanical vibration (usually 0.8-2MHz). The high-frequency vibration forms microjets in the liquid, which remove contaminants from the wafer surface. It is gentler than traditional ultrasonic cleaning and avoids damage to the wafer structure.

[0003] As is well known, the megasonic transducer resonates when the driving frequency of the drive circuit matches the natural frequency of the megasonic transducer. At the moment of resonance, the energy conversion efficiency of the megasonic transducer is at its highest. For high-efficiency systems, the megasonic transducer must be driven in the correct resonant mode to achieve maximum power transfer. The series resonant point is a commonly used resonant point for megasonic transducers. At this resonant point, the dynamic branch of the equivalent circuit model of the megasonic transducer is resistive, resulting in the highest overall electromechanical conversion efficiency. Because the megasonic transducer is a capacitive load, the driving current and voltage will not be in phase, causing reactive power loss and reducing energy conversion efficiency. Megasonic generators mainly use switching amplifiers as power amplification circuits, including half-bridge inverters, full-bridge inverters, and push-pull inverters. Their outputs are all AC square waves with multiple harmonics. Therefore, a terminal matching circuit is needed to tune and filter the AC square wave into the sine wave desired by the megasonic transducer to reduce reactive power loss.

[0004] Currently, impedance matching research mainly focuses on piezoelectric ceramics below 800kHz, with limited research on impedance matching for megasonic transducers at 1MHz. Traditional matching methods include series inductors, series capacitors, parallel inductors, parallel inductors, and T-type matching. These methods use reactive elements across the transducer to offset capacitive characteristics, making the megasonic transducer purely resistive and ensuring that the drive current and voltage are in phase. However, in actual operation, megasonic cleaning machines are significantly affected by temperature, load, and other factors. The resonant frequency of the megasonic transducer changes with load variations and prolonged operation. Traditional matching methods lack adjustment flexibility, leading to system detuning.

[0005] Furthermore, the dynamic branch current of a megasonic transducer directly reflects its mechanical vibration intensity, and at the series resonant point, the dynamic branch current is in phase with the megasonic transducer's driving voltage. In the megasonic cleaning field, monitoring and controlling the dynamic branch current of multiple piezoelectric ceramics in a balanced manner, and ensuring that the dynamic branch current is in phase with the megasonic transducer's driving voltage, can improve the energy conversion efficiency of the megasonic transducer and achieve a uniform sound field distribution. The dynamic branch current is the current within the equivalent circuit model of the megasonic transducer and cannot be directly detected. Traditional matching methods detect the transducer's driving current through LC matching and current transformers, and compare it with the transducer's driving voltage to detect the series resonant frequency. In high-frequency application environments, this is easily affected by parasitic inductance in the circuit, leading to signal distortion. Because traditional matching methods cannot directly detect the dynamic branch current reflecting the mechanical vibration intensity of the megasonic transducer, the system may become detuned under wide load conditions, leading to transducer heating, frequency lockout, and reduced system energy conversion efficiency. Summary of the Invention

[0006] The technical problem solved by this invention is that the dynamic branch current is the current within the equivalent circuit model of the megasonic transducer, and cannot be directly detected. Traditional matching methods detect the transducer drive current through LC matching and current transformers, and compare it with the transducer drive voltage to detect the series resonant frequency. In high-frequency applications, this is easily affected by the parasitic inductance of the circuit, leading to signal distortion. Because traditional matching methods cannot directly detect the dynamic branch current, which reflects the mechanical vibration intensity of the megasonic transducer, the system may become detuned under wide load conditions, leading to transducer heating, frequency lockout, and reduced system energy conversion efficiency.

[0007] To address the problems existing in the prior art, this invention proposes an impedance matching circuit for detecting the dynamic branch current of a megasonic transducer. The method includes: constructing an impedance matching circuit for detecting the dynamic branch current of a megasonic transducer; extracting the equivalent feedback voltage of the dynamic branch current through a Huygens bridge to offset the influence of the static capacitor; and then completing the impedance matching through an LC matching circuit.

[0008] The impedance matching circuit for detecting the dynamic branch current of the megasonic transducer includes a half-bridge drive circuit, an LC impedance matching network, and an equivalent circuit model of the megasonic transducer. The equivalent circuit model of the megasonic transducer includes the dynamic branch of the megasonic transducer. The half-bridge drive circuit converts DC voltage into an AC high-voltage square wave drive signal. The LC impedance matching network performs impedance transformation, tuning, and filtering. The LC impedance matching circuit is connected to the equivalent circuit model of the megasonic transducer to form a Huygens bridge, which can extract the equivalent feedback voltage of the dynamic branch current.

[0009] The beneficial effects of this invention are:

[0010] This invention achieves impedance transformation, tuning, and filtering over a wide load range, improving the energy conversion efficiency of the Megson transducer. The matching circuit design of this invention uses a Huygens bridge to directly detect the dynamic branch current inside the Megson transducer via the feedback voltage UFMB, providing direct feedback on mechanical vibration intensity. This eliminates the need for a current transformer, avoiding the influence of parasitic inductance in high-frequency circuits. In the actual control of the Megson cleaning machine, using the matching circuit of this invention, the dynamic branch current of the Megson transducer can be detected through a simple voltage detection circuit, ensuring that the feedback voltage UFMB matches the driving voltage U... in A phase difference of 180° is sufficient to ensure that the megasonic transducer operates at the series resonant point, ensuring stable and efficient output of the megasonic cleaning machine, reducing circuit complexity, and providing a convenient and accurate detection method for frequency tracking and mechanical strength vibration control of the megasonic transducer. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the modules of the present invention;

[0012] Figure 2 This is a schematic diagram of the impedance matching circuit for detecting the dynamic branch current of a megahertz transducer according to the present invention. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] This invention provides an impedance matching circuit for detecting the dynamic branch current of a megasonic transducer. Through LC matching and a Huygens bridge, the influence of the static capacitance C0 of the megasonic transducer is offset, allowing direct detection of the dynamic branch current. The impedance matching method provided by this invention can achieve tuning, filtering, and impedance transformation over a wide load range, unaffected by the load, improving energy conversion efficiency and achieving stable and efficient output from the megasonic transducer.

[0015] An impedance matching circuit for detecting the dynamic branch current of a megahertz transducer, such as... Figure 1As shown, the method includes: constructing an impedance matching circuit for detecting the dynamic branch current of a megasonic transducer, including a half-bridge drive circuit, an LC impedance matching network, and an equivalent circuit model of the megasonic transducer; the equivalent circuit model of the megasonic transducer is connected to the LC impedance matching circuit to form a Huygens bridge, used to extract the equivalent feedback voltage of the dynamic branch current; the half-bridge drive circuit is used to convert the DC input voltage into an AC high-voltage square wave drive signal; the LC impedance matching network is used to realize impedance transformation, tuning, and filtering. This invention achieves impedance transformation, tuning, and filtering over a wide load range, improving the energy conversion efficiency of the megasonic transducer.

[0016] like Figure 1 The diagram shows a module schematic of an impedance matching method for detecting the dynamic branch current of a megasonic transducer, including a half-bridge drive circuit, an LC impedance matching network, and an equivalent circuit model of the megasonic transducer. The output of the half-bridge drive circuit is connected to the input of the LC impedance matching network. The output of the LC impedance matching network is connected to the input of the equivalent circuit model of the megasonic transducer.

[0017] In this embodiment, the half-bridge drive circuit includes: field-effect transistors Q1 and Q2, capacitors C4 and C5, and a DC power supply; the positive terminal of the DC power supply is connected to the drain of Q1 and one end of capacitor C4, and the negative terminal of the DC power supply is connected to the source of Q2 and one end of capacitor C5, and then grounded; the other end of capacitor C4 is connected to the other end of capacitor C5; the source of Q1 is connected to the drain of Q2, the gate of Q1 is connected to the PWM1 signal, and the gate of Q2 is connected to the PWM2 signal.

[0018] Preferably, in this invention, both capacitor C4 and capacitor C5 are 2 volts. By controlling the alternating conduction of MOSFETs Q1 and Q2 with two pulse width modulation waves of the same amplitude but 180° phase difference, the DC input voltage is converted into an AC output square wave, which is then output to the input terminal of the impedance matching network.

[0019] In this embodiment, the LC impedance matching network includes a transformer T1, an inductor L2, a capacitor C2, a capacitor C3, a resistor R3, and a resistor R2. The first end of the transformer T1 is connected to the source of Q1, the second end of the transformer T1 is connected between capacitors C4 and C5, the third end of the transformer T1 is connected to one end of the inductor L2, and the fourth end of the transformer T1 is connected to one end of both resistors R3 and R2. The other end of the inductor L2 is connected to one end of the capacitor C2. The other end of the capacitor C2 is connected to one end of the capacitor C3, and the other end of the capacitor C3 is connected to the other end of the resistor R3. The other end of the resistor R2 is grounded.

[0020] An input drive voltage Uin is added to the LC impedance matching network, where the positive terminal of Uin is connected between capacitors C2 and C3, and the negative terminal of Uin is connected between the fourth terminal of transformer T1 and resistor R3.

[0021] In this embodiment, the equivalent circuit model of the megason transducer includes a static capacitor C0, a dynamic capacitor C1, a dynamic inductor L1, and a dynamic resistor R1; one end of C1 is connected to one end of L1, and the other end of L1 is connected to one end of R1 to form a dynamic branch; one end of the static capacitor C0 is connected to the other end of the resistor R1, and the other end of the static capacitor C0 is connected to the other end of the capacitor C1 and then grounded.

[0022] Specifically, the equivalent circuit model of the megaphone transducer includes a static capacitor C0, a dynamic capacitor C1, a dynamic inductor L1, and a dynamic resistor R1. C1, L1, and R1 form a dynamic branch. in For the driving voltage, I T The driving current is denoted by , and Im is the dynamic branch current. The static capacitance C0 of the equivalent circuit model of the megason transducer selected in this invention is 24.15. The dynamic capacitance C1 is 2.34. The dynamic inductance L1 is 8.32. The dynamic resistance R1 is 1.52. .

[0023] Based on the dynamic capacitor C1 and the dynamic inductor L1, the series resonant frequency of the megohmmeter transducer can be obtained as 1.135MHz.

[0024] In the LC impedance matching network, transformer T1 provides electrical isolation and physically isolates the high-voltage transducer circuit from the low-voltage control circuit. This invention uses a transformer with a turns ratio of 1:1.

[0025] In the aforementioned LC impedance matching network, inductor L2 is selected as 813.9 μm. The capacitor C2 is selected as 24.15. L2 and C2 resonate at the series resonant point of the megaphone transducer, achieving impedance transformation, tuning, and filtering. Since the output waveform of the half-bridge drive circuit is an AC square wave rather than a sine wave, according to Fourier transform, the square wave contains higher harmonics. L2 and C2 filter out the higher harmonics in the square wave, reducing reactive power loss and improving energy conversion efficiency.

[0026] In the LC impedance matching network, C3, R3, and R2, together with the static capacitor C0 of the equivalent circuit model of the megasonic transducer, form a Huygens bridge. Where R3C3 = R2C0, the equivalent feedback voltage of the dynamic branch current of the megasonic transducer is expressed as:

[0027] UFMB= I1R3 - I T R2=

[0028] Where I1 is the current flowing through capacitor C3 and resistor R3, and R3 is the resistance of resistor R3. T R2 is the driving current for the megason transducer, and R2 is the resistance value of resistor R2. Z represents the dynamic branch current; Z represents the load of the megaphone transducer. C0 is the series resonant frequency of the megasonite transducer, and C0 is the capacitance value of capacitor C0.

[0029] In the expression for the equivalent feedback voltage of the dynamic branch current of the megaphone transducer, since R3 and R2 are very small, We can obtain UFMB = -R2I m This method can counteract the effect of the static capacitor C0, allowing the UFMB to feed back the dynamic branch current I. m And it is unaffected by load.

[0030] In this invention, C3 is selected as 7.5. R3 uses 51m R2 is selected as 158 Where R3C3 = R2C0, UFMB can be calculated as I1R3 - I T R2. Since R2 and R3 are very small, it can be simplified to UFMB = -R2I. m =-0.158I m This method can counteract the effect of the static capacitance C0, allowing the UFMB to feed back the dynamic branch current I. m This method is unaffected by load. It can directly monitor the dynamic branch current I of the megohmmeter transducer by detecting the feedback voltage UFMB. m Feedback on the actual mechanical vibration intensity of the megasonite transducer.

[0031] This invention enables convenient detection of the dynamic branch current of a megasonic transducer. The designed impedance matching circuit with a Huygens bridge can offset the influence of the static capacitance C0 of the megasonic transducer's equivalent circuit, achieving impedance transformation, filtering, and tuning functions over a wide load range. This results in a highly stable and efficient output of the drive signal, improving energy conversion efficiency. Furthermore, this method provides a convenient and accurate detection method for frequency tracking and mechanical vibration control of megasonic transducers. In practical engineering applications, controlling the amplitude of the UFMB and maintaining a 180° phase difference with the drive voltage allows the megasonic transducer to operate at its series resonant point, ensuring long-term stable operation of the megasonic cleaning machine and improving its load adaptability.

[0032] The above-described embodiments further illustrate the purpose, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An impedance matching circuit for detecting the dynamic branch current of a megahertz transducer, characterized in that, include: An impedance matching circuit for detecting the dynamic branch current of a megasonic transducer is constructed, comprising a half-bridge drive circuit, an LC impedance matching network, and an equivalent circuit model of the megasonic transducer. The equivalent circuit model of the megasonic transducer is connected to the LC impedance matching circuit to form a Huygens bridge, which is used to extract the equivalent feedback voltage of the dynamic branch current. The half-bridge drive circuit is used to convert the DC input voltage into an AC high-voltage square wave drive signal. The LC impedance matching network is used to realize impedance transformation, tuning, and filtering.

2. The impedance matching circuit for detecting the dynamic branch current of a megahertz transducer according to claim 1, characterized in that, The half-bridge drive circuit includes: MOSFET Q1, MOSFET Q2, capacitor C4, capacitor C5, and a DC power supply; the positive terminal of the DC power supply is connected to the drain of Q1 and one end of capacitor C4, and the negative terminal of the DC power supply is connected to the source of Q2 and one end of capacitor C5 before being grounded; the other end of capacitor C4 is connected to the other end of capacitor C5; the source of Q1 is connected to the drain of Q2, the gate of Q1 is connected to the PWM1 signal, and the gate of Q2 is connected to the PWM2 signal.

3. The impedance matching circuit for detecting the dynamic branch current of a megahertz transducer according to claim 2, characterized in that, The LC impedance matching network includes transformer T1, inductor L2, capacitors C2 and C3, resistors R3 and R2. The first terminal of transformer T1 is connected to the source of Q1. The second terminal of transformer T1 is connected between capacitors C4 and C5. The third terminal of transformer T1 is connected to one end of inductor L2. The fourth terminal of transformer T1 is connected to one end of resistors R3 and R2 respectively. The other end of inductor L2 is connected to one end of capacitor C2. The other end of capacitor C2 is connected to one end of capacitor C3. The other end of capacitor C3 is connected to the other end of resistor R3. The other end of resistor R2 is grounded.

4. The impedance matching circuit for detecting the dynamic branch current of a megahertz transducer according to claim 1, characterized in that, The equivalent circuit model of the megaphone transducer includes a static capacitor C0, a dynamic capacitor C1, a dynamic inductor L1, and a dynamic resistor R1. One end of C1 is connected to one end of L1, and the other end of L1 is connected to one end of R1 to form a dynamic branch. One end of the static capacitor C0 is connected to the other end of the resistor R1, and the other end of the static capacitor C0 is connected to the other end of the capacitor C1 and then grounded.

5. The impedance matching circuit for detecting the dynamic branch current of a megahertz transducer according to claim 4, characterized in that, The connection between the equivalent circuit model of the megasonic transducer and the LC impedance matching network includes: one end of the capacitor C0 of the equivalent circuit model of the megasonic transducer is connected between capacitors C2 and C3 of the LC impedance matching network; the other end of the capacitor C0 of the equivalent circuit model of the megasonic transducer is connected to one end of the resistor R2 of the LC impedance matching network.

6. The impedance matching circuit for detecting the dynamic branch current of a megahertz transducer according to claim 5, characterized in that, The Huygens bridge consists of C3, R3, C0 and R2, where R3C3 = R2C0.

7. The impedance matching circuit for detecting the dynamic branch current of a megahertz transducer according to claim 6, characterized in that, Using a Huygens bridge, the equivalent feedback voltage of the dynamic branch current of the megasonic transducer is expressed as: UFMB= I1R3 - I T R2=-R2I m Where I1 is the current flowing through capacitor C3 and resistor R3, and R3 is the resistance of resistor R3. T R2 is the driving current for the megason transducer, and R2 is the resistance value of resistor R2. This refers to the dynamic branch current.

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