Frequency tracking current sampling circuit and electronic equipment

Abstract

The invention provides a frequency tracking current sampling circuit and electronic equipment. The frequency tracking current sampling circuit comprises a power amplifier, a first capacitor, a second capacitor, a first inductor, a second inductor, a transducer, a first zero-crossing comparator, a second zero-crossing comparator, a phase discriminator and a voltage-controlled oscillator, the power amplifier outputs sine waves, the sine waves output voltage phase information based on voltage division of the first capacitor and the second capacitor, and the sine waves output current phase information based on electromagnetic induction of the first inductor and the second inductor; the second zero-crossing comparator converts voltage phase information from sine waves into square waves, and the first zero-crossing comparator converts current phase information from sine waves into square waves; the phase discriminator is used for adjusting the output frequency of the voltage-controlled oscillator based on the phase difference between the voltage phase information of the square wave and the current phase information of the square wave; and the voltage-controlled oscillator is used for determining the working frequency of the power amplifier based on the adjusted output frequency. A current transformer can be omitted, so that the cost is reduced and the circuit structure is simplified.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and more particularly to a current sampling circuit and an electronic device for frequency tracking. Background Art

[0002] Ultrasonic transducers can be widely used in medical technology fields such as ablation and imaging. Different ultrasonic transducers have fixed resonant frequencies, and when the ultrasonic transducer operates near the resonant frequency, the working efficiency is the highest.

[0003] Currently, due to factors such as heating, aging, and load changes, the resonant frequency of the transducer will deviate from the natural frequency, resulting in the output power of the power amplifier not being fully applied to the transducer, signal distortion, and even damage to circuit components. To solve this problem, a frequency tracking circuit needs to be added.

[0004] Traditional frequency tracking circuits need to use current transformers to sample the phase of the current passing through the transducer, compare the sampled current phase with the voltage phase sampled through a voltage dividing capacitor, and feedback the result to the front-end phase detector. The phase detector adjusts the output frequency of the voltage-controlled oscillator according to the voltage-current phase difference, and the voltage-controlled oscillator controls the operating frequency of the power amplifier to follow the resonant frequency of the transducer, thereby achieving the purpose of frequency tracking. Therefore, traditional frequency tracking circuits require a current transformer for current phase sampling, with high costs and a relatively complex circuit structure. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a current sampling circuit and an electronic device for frequency tracking to reduce costs and simplify the circuit structure.

[0006] In a first aspect, an embodiment of the present invention provides a current sampling circuit with frequency tracking. The current sampling circuit with frequency tracking includes: a power amplifier, a first capacitor, a second capacitor, a first inductor, a second inductor, a transducer, a first zero-crossing comparator, a second zero-crossing comparator, a phase detector, and a voltage-controlled oscillator. One end of the power amplifier, the first capacitor, the second capacitor, and the other end of the power amplifier are connected in series in sequence. One end of the power amplifier, the first inductor, the transducer, and the other end of the power amplifier are connected in series in sequence. The first inductor and the second inductor are wound around a common magnetic core. The second inductor, the second zero-crossing comparator, and the phase detector are connected in sequence. The connection point of the first capacitor and the second capacitor, the first zero-crossing comparator, and the phase detector are connected in sequence. The phase detector, the voltage-controlled oscillator, and the power amplifier are connected in sequence. The power amplifier is configured to output a sine wave, and the sine wave outputs voltage phase information based on the voltage division of the first capacitor and the second capacitor, and outputs current phase information based on the electromagnetic induction of the first inductor and the second inductor. The first zero-crossing comparator is configured to convert the voltage phase information from a sine wave into a square wave, and the second zero-crossing comparator is configured to convert the current phase information from a sine wave into a square wave. The phase detector is configured to adjust the output frequency of the voltage-controlled oscillator based on the phase difference between the square-wave voltage phase information and the square-wave current phase information. The voltage-controlled oscillator is configured to determine the operating frequency of the power amplifier based on the adjusted output frequency.

[0007] In an alternative embodiment of the present application, the above-mentioned power amplifier includes: a MOS drive circuit, a first MOS transistor, a second MOS transistor, a third inductor, a third capacitor, and a transformer. One end of the MOS drive circuit, the first MOS transistor, the second MOS transistor, and the other end of the MOS drive circuit are connected in sequence. One end of the second MOS transistor, the third inductor, the third capacitor, the transformer, and the other end of the second MOS transistor are connected in sequence. The MOS drive circuit, the first MOS transistor, and the second MOS transistor are configured to generate a square wave. The third inductor and the third capacitor resonate to convert the square wave into a sine wave, and the sine wave is coupled to the secondary through the transformer.

[0008] In an alternative embodiment of the present application, the above-mentioned first capacitor, second capacitor, first inductor, second inductor, and transducer are all disposed on the secondary of the transformer.

[0009] In an alternative embodiment of the present application, the above-mentioned voltage-controlled oscillator is configured to determine the operating frequency of the MOS drive circuit based on the adjusted output frequency.

[0010] In an alternative embodiment of the present application, the above-mentioned phase detector includes an exclusive-OR gate and a flip-flop.

[0011] In an alternative embodiment of the present application, if the phase of the voltage phase information of the square wave leads the phase of the current phase information of the square wave, the phase discriminator is used to reduce the output frequency of the voltage-controlled oscillator; if the phase of the voltage phase information of the square wave is the same as the phase of the current phase information of the square wave, the phase discriminator is used to keep the output frequency of the voltage-controlled oscillator unchanged; if the phase of the voltage phase information of the square wave lags the phase of the current phase information of the square wave, the phase discriminator is used to increase the output frequency of the voltage-controlled oscillator.

[0012] In an alternative embodiment of the present application, if the phase of the voltage phase information of the square wave is the same as the phase of the current phase information of the square wave, the output voltage of the phase discriminator is determined as the reference voltage.

[0013] In an alternative embodiment of the present application, the above-mentioned phase discriminator is further used to determine whether the operating frequency of the power amplifier is the same as the resonant frequency of the transducer based on the phase difference between the voltage phase information of the square wave and the current phase information of the square wave.

[0014] In an alternative embodiment of the present application, if the phase of the voltage phase information of the square wave leads the phase of the current phase information of the square wave, the phase discriminator is further used to determine that the operating frequency of the power amplifier is greater than the resonant frequency of the transducer; if the phase of the voltage phase information of the square wave is the same as the phase of the current phase information of the square wave, the phase discriminator is further used to determine that the operating frequency of the power amplifier is equal to the resonant frequency of the transducer; if the phase of the voltage phase information of the square wave lags the phase of the current phase information of the square wave, the phase discriminator is further used to determine that the operating frequency of the power amplifier is less than the resonant frequency of the transducer.

[0015] In a second aspect, an embodiment of the present invention further provides an electronic device, and the electronic device includes the above-mentioned current sampling circuit for frequency tracking.

[0016] The embodiments of the present invention bring the following beneficial effects:

[0017] The embodiments of the present invention provide a current sampling circuit for frequency tracking and an electronic device. By winding the second inductor and the third inductor around the same magnetic core for current sampling, the current transformer can be omitted, thereby reducing costs and simplifying the circuit structure.

[0018] Other features and advantages of the present disclosure will be described in the following specification, or some features and advantages can be inferred from the specification without doubt, or can be known by implementing the above technologies of the present disclosure.

[0019] To make the above objects, features, and advantages of the present disclosure more obvious and understandable, the following preferred embodiments are specifically described below in conjunction with the accompanying drawings. Description of the Drawings

[0020] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 FIG. is a schematic structural diagram of a current sampling circuit for frequency tracking provided by an embodiment of the present invention;

[0022] Figure 2 FIG. is a schematic structural diagram of another current sampling circuit for frequency tracking provided by an embodiment of the present invention;

[0023] Figure 3 FIG. is a schematic structural diagram of an electronic device provided by an embodiment of the present invention. Specific Embodiments

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the present invention with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0025] Currently, traditional frequency tracking circuits need to use current transformers to perform phase sampling on the current passing through the transducer. The sampled current phase is compared with the voltage phase sampled through the voltage-dividing capacitor, and the result is fed back to the front-end phase discriminator. The phase discriminator adjusts the output frequency of the voltage-controlled oscillator according to the phase difference between the voltage and current, and the voltage-controlled oscillator controls the operating frequency of the power amplifier to follow the resonant frequency of the transducer, thereby achieving the purpose of frequency tracking. Therefore, traditional frequency tracking circuits require a current transformer for current phase sampling, which has a relatively high cost and a relatively complex circuit structure.

[0026] Based on this, a current sampling circuit for frequency tracking and an electronic device provided by an embodiment of the present invention can be applied to scenarios using ultrasonic waves (such as ultrasonic transducers in the field of implantable medicine). In this embodiment, there is no need to set a current transformer, and current sampling can be performed by winding the first inductor and the second inductor around a common magnetic core, thereby reducing costs and simplifying the circuit structure.

[0027] To facilitate the understanding of this embodiment, first, a current sampling circuit for frequency tracking disclosed in the embodiments of the present invention will be introduced in detail.

[0028] Embodiment 1:

[0029] See Figure 1 The structural schematic diagram of a current sampling circuit with frequency tracking shown in Figure 1 . The current sampling circuit with frequency tracking includes: a power amplifier, a first capacitor C1, a second capacitor C2, a first inductor L1, a second inductor L2, a transducer TR, a first zero-crossing comparator U1, a second zero-crossing comparator U2, a phase discriminator, and a voltage-controlled oscillator;

[0030] One end of the power amplifier, the first capacitor C1, the second capacitor C2, and the other end of the power amplifier are connected in series in sequence. One end of the power amplifier, the first inductor L1, the transducer TR, and the other end of the power amplifier are connected in series in sequence. The first inductor L1 and the second inductor L2 are wound around a common magnetic core; the second inductor L2, the second zero-crossing comparator U2, and the phase discriminator are connected in sequence. The connection point of the first capacitor C1 and the second capacitor C2, the first zero-crossing comparator U1, and the phase discriminator are connected in sequence. The phase discriminator, the voltage-controlled oscillator, and the power amplifier are connected in sequence;

[0031] The power amplifier is used to output a sine wave. The sine wave outputs voltage phase information VS based on the voltage division of the first capacitor C1 and the second capacitor C2, and outputs current phase information IS based on the electromagnetic induction of the first inductor L1 and the second inductor L2; the first zero-crossing comparator U1 is used to convert the voltage phase information VS from a sine wave to a square wave, and the second zero-crossing comparator U2 is used to convert the current phase information IS from a sine wave to a square wave; the phase discriminator is used to adjust the output frequency of the voltage-controlled oscillator based on the phase difference between the square-wave voltage phase information VS and the square-wave current phase information IS; the voltage-controlled oscillator is used to determine the operating frequency of the power amplifier based on the adjusted output frequency.

[0032] In this embodiment, the output voltage phase information VS can be sampled by the voltage division of the first capacitor C1 and the second capacitor C2, and the current phase information IS in this embodiment can be sampled by the electromagnetic induction of the first inductor L1 and the second inductor L2. Therefore, in this embodiment, there is no need to set a current transformer to sample the current phase information IS, thereby reducing costs and simplifying the circuit structure.

[0033] In this embodiment, after sampling the voltage phase information VS and the current phase information IS, the first zero-crossing comparator U1 and the second zero-crossing comparator U2 can respectively convert the voltage phase information VS and the current phase information IS from a sine wave to a square wave. The phase discriminator can determine the phase difference between the square-wave voltage phase information VS and the square-wave current phase information IS. The phase discriminator adjusts the output frequency of the voltage-controlled oscillator according to the above phase difference, and the voltage-controlled oscillator determines the operating frequency of the power amplifier according to the adjusted output frequency, so that the operating frequency of the power amplifier changes following the resonant frequency of the transducer, thereby realizing the function of frequency tracking.

[0034] An embodiment of the present invention provides a current sampling circuit for frequency tracking. By winding a second inductor and a third inductor around a common magnetic core for current sampling, a current transformer can be omitted, thereby reducing costs and simplifying the circuit structure.

[0035] Embodiment 2:

[0036] This embodiment provides a current sampling circuit for frequency tracking, which is implemented on the basis of the above embodiment. Refer to Figure 2 the structural schematic diagram of another current sampling circuit for frequency tracking shown in the figure. The power amplifier includes: a MOS driving circuit, a first MOS transistor Q1, a second MOS transistor Q2, a third inductor L3, a third capacitor C3, and a transformer T1; one end of the MOS driving circuit, the first MOS transistor Q1, the second MOS transistor Q2, and the other end of the MOS driving circuit are connected in sequence, and one end of the second MOS transistor Q2, the third inductor L3, the third capacitor C3, the transformer T1, and the other end of the second MOS transistor Q2 are connected in sequence; the MOS driving circuit, the first MOS transistor Q1, and the second MOS transistor Q2 are used to generate square waves; the third inductor L3 and the third capacitor C3 resonate to convert the square waves into sine waves, and the sine waves are coupled to the secondary through the transformer T1.

[0037] As Figure 2 shown in the figure, in this embodiment, the third inductor L3 and the third capacitor C3 can resonate to convert the 50Khz square waves generated by the first MOS transistor Q1 and the second MOS transistor Q2 into sine waves, and the sine waves are coupled to the secondary through the transformer T1.

[0038] In some embodiments, the first capacitor C1, the second capacitor C2, the first inductor L1, the second inductor L2, and the transducer TR are all arranged on the secondary of the transformer T1.

[0039] As Figure 2 shown in the figure, the sine waves coupled to the secondary are divided by the first capacitor C1 and the second capacitor C2 to generate voltage phase information VS. The voltage phase information VS is input to the positive phase terminal of the first zero-crossing comparator U1, and the first zero-crossing comparator U1 can convert the voltage phase information VS from a sine wave into a square wave.

[0040] As Figure 2 shown in the figure, the sine waves coupled to the secondary are applied to the transducer TR through the first inductor L1. Since the second inductor L2 and the first inductor L1 are wound around a common magnetic core together, the second inductor L2 and the first inductor L1 can be regarded as a transformer, and the second inductor L2 will couple the current phase information IS of the first inductor L1. The current phase information IS is input to the positive phase terminal of the second zero-crossing comparator U2, and the second zero-crossing comparator U2 can convert the current phase information IS from a sine wave into a square wave.

[0041] In some embodiments, the phase detector includes an exclusive - OR gate and a flip - flop. The voltage phase information VS and the current phase information IS of the square wave in this embodiment can be transmitted to the phase detector, and the phase detector can adjust the output frequency of the voltage - controlled oscillator according to the phase difference between the two.

[0042] In addition, in some embodiments, the phase detector is further configured to determine whether the operating frequency of the power amplifier is the same as the resonant frequency of the transducer based on the phase difference between the voltage phase information and the current phase information of the square wave.

[0043] In this embodiment, the phase detector can also determine whether the operating frequency of the power amplifier is the same as the resonant frequency of the transducer based on the phase difference between the voltage phase information and the current phase information of the square wave.

[0044] The following is a discussion in different cases:

[0045] (1) The phase of the voltage phase information of the square wave is the same as the phase of the current phase information of the square wave.

[0046] In some embodiments, if the phase of the voltage phase information of the square wave is the same as the phase of the current phase information of the square wave, the phase detector is configured to keep the output frequency of the voltage - controlled oscillator unchanged.

[0047] In some embodiments, if the phase of the voltage phase information of the square wave is the same as the phase of the current phase information of the square wave, the phase detector is further configured to determine that the operating frequency of the power amplifier is equal to the resonant frequency of the transducer.

[0048] In some embodiments, if the phase of the voltage phase information of the square wave is the same as the phase of the current phase information of the square wave, the output voltage of the phase detector is determined to be the reference voltage.

[0049] If the phase of the voltage phase information VS of the square wave is the same as the phase of the current phase information IS of the square wave, it indicates that the operating frequency of the power amplifier is consistent with the resonant frequency of the transducer TR. The equivalent impedance of the transducer TR is the smallest and is purely resistive. The current flowing through the transducer is the largest and the efficiency is the highest. At this time, the output voltage of the phase detector is the reference voltage. If it is higher than the reference voltage, the output frequency of the voltage - controlled oscillator increases, and vice versa, the output frequency decreases.

[0050] (2) The phase of the voltage phase information of the square wave is ahead of the phase of the current phase information of the square wave.

[0051] In some embodiments, if the phase of the voltage phase information of the square wave is ahead of the phase of the current phase information of the square wave, the phase detector is configured to decrease the output frequency of the voltage - controlled oscillator.

[0052] In some embodiments, if the phase of the voltage phase information of the square wave is ahead of the phase of the current phase information of the square wave, the phase detector is further configured to determine that the operating frequency of the power amplifier is greater than the resonant frequency of the transducer.

[0053] If the phase of the voltage phase information of the square wave is ahead of the phase of the current phase information of the square wave, it indicates that the operating frequency of the power amplifier is greater than the resonant frequency of the transducer TR, the circuit is inductive, and it is necessary to reduce the operating frequency of the power amplifier.

[0054] Since the phase of the voltage phase information VS of the square wave is ahead of the phase of the current phase information IS of the square wave, the two square wave phase information, one after the other, pass through a phase detector composed of an exclusive-OR gate and a flip-flop. The output voltage of the phase detector will be lower than the reference voltage, the output frequency of the voltage-controlled oscillator decreases, and the operating frequency of the power amplifier it controls decreases synchronously until it converges to the resonant frequency of the transducer TR. After that, the phase of the detected voltage phase information VS of the square wave and the phase of the current phase information IS of the square wave are also basically the same.

[0055] (3) The phase of the voltage phase information of the square wave lags behind the phase of the current phase information of the square wave.

[0056] In some embodiments, if the phase of the voltage phase information of the square wave lags behind the phase of the current phase information of the square wave, the phase detector is configured to increase the output frequency of the voltage-controlled oscillator.

[0057] In some embodiments, if the phase of the voltage phase information of the square wave lags behind the phase of the current phase information of the square wave, the phase detector is further configured to determine that the operating frequency of the power amplifier is less than the resonant frequency of the transducer.

[0058] If the phase of the voltage phase information VS of the square wave lags behind the phase of the current phase information IS of the square wave, it indicates that the operating frequency of the power amplifier is less than the resonant frequency of the transducer TR, the circuit is capacitive, and it is necessary to increase the operating frequency. The phase of the voltage phase information VS of the square wave passes through the phase detector with the phase of the current phase information IS of the square wave. The voltage output by the phase detector is higher than the reference voltage, and as a result, the output frequency of the voltage-controlled oscillator increases, and the operating frequency of the power amplifier it controls increases synchronously until it converges to the resonant frequency of the transducer TR. After that, the phase of the detected voltage phase information VS of the square wave and the phase of the current phase information IS of the square wave are also basically the same.

[0059] In some embodiments, the voltage-controlled oscillator is configured to determine the operating frequency of the MOS drive circuit based on the adjusted output frequency.

[0060] Such as Figure 2As shown, the voltage-controlled oscillator can determine the operating frequency of the MOS drive circuit based on the adjusted output frequency, so that the operating frequency of the power amplifier changes following the resonant frequency of the transducer, thereby realizing the function of frequency tracking.

[0061] For the current sampling circuit for frequency tracking provided by the embodiments of the present invention, current sampling is performed by winding the second inductor and the third inductor around the same magnetic core, which can eliminate the current transformer, thereby reducing costs and simplifying the circuit structure. In addition, the phase detector can determine the phase difference between the voltage phase information VS of the square wave and the current phase information IS of the square wave. The phase detector adjusts the output frequency of the voltage-controlled oscillator according to the above phase difference. The voltage-controlled oscillator determines the operating frequency of the power amplifier based on the adjusted output frequency, so that the operating frequency of the power amplifier changes following the resonant frequency of the transducer, thereby realizing the function of frequency tracking.

[0062] Embodiment 3:

[0063] The embodiments of the present invention also provide an electronic device. Refer to Figure 3 the structural schematic diagram of an electronic device as shown. The electronic device includes the current sampling circuit for frequency tracking provided by the foregoing embodiments.

[0064] Those skilled in the art can clearly understand that for the convenience and brevity of description, the specific working processes of the above-described systems and / or devices can refer to the corresponding processes in the foregoing method embodiments and will not be elaborated herein.

[0065] In addition, in the description of the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", and "couple" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0066] If a function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or a part of this technical solution can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods of various embodiments of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs.

[0067] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0068] Finally, it should be noted that the above embodiments are only specific embodiments of the present invention, used to illustrate the technical solutions of the present invention, rather than limiting them. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that any person skilled in the technical field of the present invention can still modify the technical solutions recorded in the foregoing embodiments or easily think of changes, or perform equivalent replacements for some of the technical features; and these modifications, changes, or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention and should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims

1. A current sampling circuit for frequency tracking, characterized in that, the current sampling circuit for frequency tracking includes: a power amplifier, a first capacitor, a second capacitor, a first inductor, a second inductor, a transducer, a first zero-crossing comparator, a second zero-crossing comparator, a phase discriminator and a voltage-controlled oscillator; one end of the power amplifier, the first capacitor, the second capacitor and the other end of the power amplifier are connected in series in sequence, one end of the power amplifier, the first inductor, the transducer and the other end of the power amplifier are connected in series in sequence, and the first inductor and the second inductor are wound around a common magnetic core; the second inductor, the second zero-crossing comparator and the phase discriminator are connected in sequence, the connection point of the first capacitor and the second capacitor, the first zero-crossing comparator and the phase discriminator are connected in sequence, and the phase discriminator, the voltage-controlled oscillator and the power amplifier are connected in sequence; the power amplifier is used to output a sine wave, and the sine wave outputs voltage phase information based on the voltage division of the first capacitor and the second capacitor, and the sine wave outputs current phase information based on the electromagnetic induction of the first inductor and the second inductor; the first zero-crossing comparator is used to convert the voltage phase information from a sine wave into a square wave, and the second zero-crossing comparator is used to convert the current phase information from a sine wave into a square wave; the phase discriminator is used to adjust the output frequency of the voltage-controlled oscillator based on the phase difference between the voltage phase information of the square wave and the current phase information of the square wave; the voltage-controlled oscillator is used to determine the operating frequency of the power amplifier based on the adjusted output frequency.

2. The current sampling circuit for frequency tracking according to claim 1, characterized in that, the power amplifier includes: a MOS drive circuit, a first MOS transistor, a second MOS transistor, a third inductor, a third capacitor and a transformer; one end of the MOS drive circuit, the first MOS transistor, the second MOS transistor and the other end of the MOS drive circuit are connected in sequence, and one end of the second MOS transistor, the third inductor, the third capacitor, the transformer and the other end of the second MOS transistor are connected in sequence; the MOS drive circuit, the first MOS transistor and the second MOS transistor are used to generate a square wave; the third inductor and the third capacitor resonate to convert the square wave into a sine wave, and the sine wave is coupled to the secondary through the transformer.

3. The current sampling circuit for frequency tracking according to claim 2, characterized in that, the first capacitor, the second capacitor, the first inductor, the second inductor and the transducer are all arranged on the secondary of the transformer.

4. The current sampling circuit for frequency tracking according to claim 2, characterized in that, the voltage-controlled oscillator is used to determine the operating frequency of the MOS drive circuit based on the adjusted output frequency.

5. The current sampling circuit for frequency tracking according to claim 1, characterized in that, the phase discriminator includes an exclusive-OR gate and a flip-flop.

6. The current sampling circuit for frequency tracking according to claim 1, characterized in that, If the phase of the voltage phase information of the square wave leads the phase of the current phase information of the square wave, the phase detector is used to reduce the output frequency of the voltage-controlled oscillator; If the phase of the voltage phase information of the square wave is the same as the phase of the current phase information of the square wave, the phase detector is used to keep the output frequency of the voltage-controlled oscillator unchanged; If the phase of the voltage phase information of the square wave lags the phase of the current phase information of the square wave, the phase detector is used to increase the output frequency of the voltage-controlled oscillator.

7. The current sampling circuit with frequency tracking according to claim 1, wherein, If the phase of the voltage phase information of the square wave is the same as the phase of the current phase information of the square wave, the output voltage of the phase detector is determined as the reference voltage.

8. The current sampling circuit with frequency tracking according to claim 1, wherein, The phase detector is further used to judge whether the operating frequency of the power amplifier is the same as the resonant frequency of the transducer based on the phase difference between the voltage phase information of the square wave and the current phase information of the square wave.

9. The current sampling circuit with frequency tracking according to claim 8, wherein, If the phase of the voltage phase information of the square wave leads the phase of the current phase information of the square wave, the phase detector is further used to determine that the operating frequency of the power amplifier is greater than the resonant frequency of the transducer; If the phase of the voltage phase information of the square wave is the same as the phase of the current phase information of the square wave, the phase detector is further used to determine that the operating frequency of the power amplifier is equal to the resonant frequency of the transducer; If the phase of the voltage phase information of the square wave lags the phase of the current phase information of the square wave, the phase detector is further used to determine that the operating frequency of the power amplifier is less than the resonant frequency of the transducer.

10. An electronic device, wherein, The electronic device includes the current sampling circuit with frequency tracking according to any one of claims 1-9.

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