WO2019113789A1

WO2019113789A1 - Frequency locking circuit and control method therefor

Info

Publication number: WO2019113789A1
Application number: PCT/CN2017/115712
Authority: WO
Inventors: 杨明
Original assignee: 深圳和而泰数据资源与云技术有限公司
Priority date: 2017-12-12
Filing date: 2017-12-12
Publication date: 2019-06-20
Also published as: CN108702132A

Abstract

A frequency locking circuit and a control method therefor. The frequency locking circuit comprises: a switch circuit (101), a sampling circuit (102), a controller (103), and an oscillating circuit (104). An input end (101b) of the switch circuit (101) is connected to the oscillating circuit (104); an output end (101c) of the switch circuit (101) is connected to a first end of the sampling circuit (102); a control signal output end of the controller (103) is connected to a control end (101a) of the switch circuit (101); a detection signal input end of the controller (103) is respectively connected to the output end (101c) of the switch circuit (101) and the first end of the sampling circuit (102); a second end of the sampling circuit (102) is grounded. The controller (103) is configured to: control on/off of the switch circuit (101) according to a preset control frequency band, detect a voltage drop value corresponding to the sampling circuit (102), obtain a control frequency corresponding to the maximum voltage drop value, and lock the obtained control frequency to control on/off of the switch circuit (101). The frequency locking circuit can lock the oscillating circuit at a resonance frequency.

Description

Frequency locking circuit and control method thereof

Technical field

The embodiments of the present invention relate to the field of electronic circuit technologies, and in particular, to a frequency locking circuit and a control method thereof.

Background technique

The humidifying device is usually composed of an oscillating circuit including a atomizing sheet controlled by a controller. The humidifying principle is that the liquid water molecular structure is broken up by the high frequency oscillating property of the atomizing sheet to generate ultrafine particles and negative oxygen ions. fog.

In practical applications, due to the long-term use of the atomized sheet in the water, it is easy to cause its parameter to change, or due to the parameter error of the circuit component, etc., the resonance frequency of the controller output control oscillation circuit will be deviated, resulting in the atomization sheet. The spray effect is worse.

Summary of the invention

The purpose of the present application is to provide a frequency locking circuit and a control method thereof for solving the problem that the resonant frequency is easily deviated, so that the oscillating circuit cannot be in a resonant state.

To achieve the above objective, in a first aspect, an embodiment of the present application provides a frequency locking circuit, where the frequency locking circuit includes: a switching circuit, a sampling circuit, a controller, and an oscillating circuit.

An input end of the switch circuit is connected to the oscillating circuit, an output end of the switch circuit is connected to a first end of the sampling circuit, and a control signal output end of the controller is connected to a control end of the switch circuit, The detection signal input end of the controller is respectively connected to the output end of the switch circuit and the first end of the sampling circuit, and the second end of the sampling circuit is grounded;

The controller is configured to: control the on/off of the switch circuit according to a preset control frequency band, and detect a voltage drop value corresponding to the sampling circuit, obtain a control frequency corresponding to the maximum voltage drop value, and lock the acquired The control frequency controls on and off of the switching circuit.

Optionally, the sampling circuit is a sampling resistor.

Optionally, the switch circuit includes: a first resistor, a second resistor, and a switch tube;

One end of the first resistor is connected to a control signal output end of the controller, and the other end of the first resistor is respectively connected to one end of the second resistor and a control end of the switch tube; the input of the switch tube The end is connected to the oscillating circuit, and the output end of the switch tube is respectively connected to the first end of the sampling circuit and the detection signal input end of the controller; the other end of the second resistor is grounded.

Optionally, the oscillating circuit includes: a first inductor, a second inductor, a first capacitor, a second capacitor, and an atomizing sheet;

One end of the first inductor is connected to the power source, and the other end of the first inductor is respectively connected to one end of the first capacitor and an input end of the switch circuit; the other end of the first capacitor is respectively connected to the second inductor And a second capacitor;

One end of the atomization piece is connected to the second inductor, and the other end is connected to the second capacitor and grounded.

Optionally, the method further includes a filter circuit, where the filter circuit includes: a third resistor and a third capacitor;

One end of the third resistor is respectively connected to the first end of the sampling circuit and the output end of the switch tube, and the other end of the third resistor is connected to one end of the third capacitor and a detection signal of the controller An input end; the other end of the third capacitor is grounded.

In a second aspect, the embodiment of the present application further provides a method for controlling a frequency locking circuit, where the frequency locking circuit is a frequency locking circuit as described above, and the method includes:

Controlling the on/off of the switch circuit according to a preset control frequency band, and detecting a voltage drop value corresponding to the sampling circuit, and obtaining a control frequency corresponding to the maximum voltage drop value;

The lock controls the on and off of the switch circuit according to the acquired control frequency.

Optionally, the controlling the on/off of the switch circuit according to the preset control frequency band, and detecting the voltage drop value corresponding to the sampling circuit, and acquiring the control frequency corresponding to the maximum voltage drop value, specifically including:

Step a, outputting a first oscillation frequency to the switch circuit in a preset control frequency band, and acquiring a first voltage drop value of the sampling circuit according to the first oscillation frequency, and saving the first oscillation frequency and the First pressure drop value;

Step b: decreasing or increasing the first oscillation frequency according to a preset frequency difference to obtain a second oscillation frequency, and acquiring a second voltage drop value of the sampling circuit according to the second oscillation frequency;

Step c, determining whether the second voltage drop value is greater than the first voltage drop value, and if so, replacing the second oscillation frequency and the second voltage drop value with the saved first oscillation frequency and the first The voltage drop value is obtained until the preset control frequency band is obtained such that the sampling circuit generates a control frequency corresponding to the maximum voltage drop value.

Optionally, the preset control frequency band is [f ₀ (1-a%), f ₀ (1+a%)], where f ₀ refers to a resonance of the oscillation circuit in the frequency locking circuit. Frequency, a is any parameter within the preset range.

In the embodiment of the present application, the switching of the switching circuit is controlled by outputting the control frequency in the preset control frequency band, and when the switching circuit is turned on and off for each control frequency, the voltage drop value of the sampling circuit corresponding to each control frequency is detected. Finally, the maximum voltage drop value of the sampling circuit is obtained, and the corresponding control frequency is obtained according to the maximum voltage drop value, so that the controller can control the switching circuit to be turned on and off according to the control frequency, and the oscillation circuit is locked at the resonance frequency to maintain the resonance state. Therefore, on the one hand, the embodiment saves the manual debugging link, saves the production cost, improves the production efficiency, and on the other hand, enables the spray device with the frequency locking circuit to have a better spray effect and improve the user experience. .

DRAWINGS

The one or more embodiments are exemplified by the accompanying drawings in the accompanying drawings, and FIG. The figures in the drawings do not constitute a scale limitation unless otherwise stated.

1 is a schematic block diagram of a frequency locking circuit provided by an embodiment of the present application;

2 is a schematic structural diagram of a frequency locking circuit according to an embodiment of the present application;

3 is a schematic block diagram of a frequency locking circuit according to another embodiment of the present application;

4 is a schematic structural diagram of a frequency locking circuit according to another embodiment of the present application;

FIG. 5 is a schematic flowchart of a method for controlling a frequency locking circuit according to an embodiment of the present disclosure;

6 is a schematic flowchart of a method for acquiring a preset control frequency corresponding to a maximum voltage drop value in a method for controlling a frequency locking circuit according to an embodiment of the present disclosure;

FIG. 7 is a schematic flow chart of another method for obtaining a preset control frequency corresponding to a maximum voltage drop value in a method for controlling a frequency locking circuit according to an embodiment of the present disclosure.

Detailed ways

The technical solutions in the embodiments of the present application are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present application. The specific embodiments are only used to explain the present application and are not intended to limit the application.

Please refer to FIG. 1. FIG. 1 is a schematic block diagram of a frequency locking circuit according to an embodiment of the present application. As shown in FIG. 1, the frequency locking circuit includes: a switch circuit 101, a sampling circuit 102, a controller 103, and an oscillating power Road 104.

The switch circuit 101 includes a control terminal 101a, an input terminal 101b, and an output terminal 101c. The input terminal 101b of the switch circuit 101 is connected to the oscillation circuit 104. The output terminal 101c of the switch circuit 101 is connected to the first end of the sampling circuit 102. The control terminal 101a is connected to the control signal output terminal of the controller 103 for outputting a control signal. When the control signal controls the switch circuit 101 to be turned on, the power supply passes through the oscillation circuit 104 to control the oscillation circuit 104 to oscillate.

The detection signal input terminals of the controller 103 are respectively connected to the output terminal 101c of the switch circuit 101 and the first terminal of the sampling circuit 102. When the switch circuit 101 is turned on, the controller 103 detects a voltage drop value corresponding to the sampling circuit 102.

In this embodiment, the oscillating circuit 104 can be an LC oscillating circuit, and the controller 103 can be a single chip microcomputer. According to the LC series circuit resonance, the impedance is the smallest and the current is the largest. Therefore, when the voltage drop of the sampling circuit 102 is larger, the oscillation circuit is closer to the resonance state.

Therefore, the purpose of the frequency-locked circuit of the oscillating circuit 104 is to detect the maximum voltage drop value of the sampling circuit 102, obtain a corresponding control frequency according to the maximum voltage drop value, and control the switching of the switch circuit 101 according to the control frequency. The operating frequency of the oscillating circuit 104 is controlled to operate the oscillating circuit 104 in a resonant state.

The working principle of the frequency locking circuit is: the controller 103 outputs a control signal to control the switching circuit 101 to be turned on and off, thereby controlling the oscillation of the oscillation circuit 104, and at the same time, detecting the voltage of the sampling circuit 102 at the control frequency corresponding to the control signal. The value is lowered, and in this process, the magnitude of the control frequency of the control signal output from the controller 103 is updated, and the voltage drop value of the sampling circuit 102 is detected each time the control frequency of the control signal is updated. When the updated control frequency exceeds the preset control frequency range, the maximum voltage drop value of the sampling circuit 102 is obtained from all the detected voltage drop values, and the impedance circuit 104 has the minimum impedance and current when the resonant circuit 104 is in the resonant state. The biggest feature, therefore, the greater the voltage drop across the sampling circuit 102, the closer the oscillating circuit 104 is to the resonant state. Thereby, the maximum voltage drop value of the sampling circuit 102 is obtained, and the control frequency corresponding to the maximum voltage drop value is obtained. When the controller 103 controls the oscillation circuit 104 to oscillate via the switching circuit 101 at the control frequency, the oscillation circuit 104 can Working in a resonant state. The preset control frequency range may be [f ₀ (1-a%), f ₀ (1+a%)], where f ₀ refers to the resonant frequency of the oscillating circuit 104, and a is a preset. Any parameter within the range, which may be a greater than 0 and less than 100. In this embodiment, a can be specifically taken as 10, that is, the preset control frequency range is [f ₀ (1-10%), f ₀ (1+10%)], and the f ₀ can be calculated according to the following formula. Wherein L refers to the equivalent inductance value of the inductance in the oscillation circuit 104, and C refers to the equivalent capacitance value of the capacitance and the atomization sheet in the oscillation circuit 104. Among them, the atomizing sheet can be equivalent to a capacitor.

Referring to FIG. 2, in some embodiments, the switch circuit 101 includes a first resistor R1, a second resistor R2, and a switch transistor Q1. One end of the first resistor R1 is connected to the control signal output end of the controller 103, and the other end of the first resistor R1 is respectively connected to one end of the second resistor R2 and the control end of the switch tube Q1; the other end of the second resistor R2 is grounded; The input end of the switch tube Q1 is connected to the oscillating circuit 104; the output end of the switch tube is respectively connected to the first end of the sampling circuit 102 and the detection signal input end of the controller 103. In this embodiment, the switch tube Q1 may be a triode. When it is a triode, the control end is the base of the triode, the input end is the collector of the triode, and the output end is the emitter of the triode. The switch Q1 can also be a field effect transistor, such as a MOS field effect transistor. When it is a field effect transistor, the control terminal is the gate of the FET, and the input terminal is the drain of the FET, and the output is the output. The end is the source of the FET.

The sampling circuit 102 is a sampling resistor R3. The specific process of detecting the voltage drop value of the sampling resistor R3 includes detecting the voltage of the sampling resistor R3 after the switching transistor Q1 is turned on, and the voltage is sent to the AD detection signal input port WH_AD of the controller 103. It should be noted that when the switching transistor Q1 is a triode, the triode will be turned on only when the voltage difference between the base and the emitter is greater than a preset threshold. When the switching transistor Q1 is a field effect transistor, only The FET is turned on when the gate-to-source voltage difference is greater than a predetermined threshold. Therefore, the resistance of the sampling resistor R3 is not too large here, and the resistance of the sampling resistor R3 can be reasonably set according to the parameters of each component in the circuit.

In this embodiment, the average value algorithm may be used to calculate the voltage drop value of the sampling resistor R3. Specifically, the controller 103 outputs a control signal to the switch circuit 101, and when the switch circuit 101 is controlled to be turned on and off by the control frequency corresponding to the control signal. At the control frequency, the voltage of the sampling resistor R3 is detected a plurality of times, and finally, the detected plurality of voltages are averaged to obtain a voltage drop value of the sampling resistor R3 corresponding to the control frequency.

The oscillating circuit 104 includes a first inductor L1, a second inductor L2, a first capacitor C1, a second capacitor C2, and an atomizing sheet W1. One end of the first inductor L1 is connected to the power source, and the other end of the first inductor L1 is respectively connected to one end of the first capacitor C1 and the input end 101b of the switch circuit 101, and the other end of the first capacitor C1 is respectively connected to the second inductor L2 and the first The second capacitor C2 has one end connected to the second inductor L2 and the other end connected to the second capacitor C2 and the ground.

In other embodiments, referring to FIG. 3, the frequency locking circuit further includes a filtering circuit 105. One end of the filter circuit 105 is connected between the switch circuit 101 and the sampling circuit 102, and the other end thereof is connected to the controller 103. Specifically, one end of the filter circuit 105 is connected to the output end 101c of the switch circuit 101 and the first end of the sampling circuit 102. The other end thereof is connected to the detection signal input terminal of the controller 103. Here, when the voltage drop signal generated by the sampling circuit 102 is input to the controller 103, it is filtered by the filter circuit 105 to filter out the clutter in the voltage drop signal, so that the controller 103 can accurately detect the sampling. The voltage drop of resistor R3 allows for a more precise control frequency.

Referring to FIG. 4, in some embodiments, the filter circuit 105 includes a third resistor R4 and a third capacitor C3. The first end of the third resistor R4 is connected to the first end of the sampling resistor R3 and the output end of the switch tube Q1, and the other end of the third resistor R4 is connected to one end of the third capacitor C3 and the detection signal input end of the controller 103; The other end of the third capacitor C3 is grounded. Here, the voltage across the sampling resistor R3 is filtered by the third resistor R4 and the third capacitor C3, and then output to the detection signal input port WH_AD of the controller 103, and the voltage drop value of the sampling resistor R3 is obtained by detection.

It can be understood by those skilled in the art that the description of the function of the frequency-locked circuit disclosed in the embodiment of the present application (such as filtering, etc.) can be adjusted, changed or replaced with the specific functional circuit module according to the actual situation. Such technical solutions for adjustment, modification or replacement are all within the scope disclosed in the embodiments of the present application.

It should be noted that the frequency locking circuit provided by the embodiment of the present application can be applied to a spray device, which can be a humidifier, a spray beauty device, or the like.

The working principle of the spraying device is that the controller 103 first operates in a frequency sweeping mode, in which the controller 103 outputs a control signal to control the switching circuit 101 to be turned on and off, thereby controlling the oscillation circuit 104 to oscillate, and at the same time, in the control At the control frequency corresponding to the signal, the voltage drop value of the sampling circuit 102 is detected. In this process, the magnitude of the control frequency of the control signal output by the controller 103 is updated, and the sampling circuit is detected after each control frequency of the control signal is updated. The pressure drop value of 102. When the updated control frequency exceeds the preset control frequency range, the maximum voltage drop value of the sampling circuit 102 is obtained from all the detected voltage drop values, and the control frequency corresponding to the maximum voltage drop value is obtained, thereby The frequency sweep mode is entered and the frequency lock mode is entered. In the frequency lock mode, the output signal of the controller 103 is controlled by the switch circuit 101 to control the oscillation circuit 104 to oscillate. The frequency of the control signal is the control frequency corresponding to the maximum voltage drop value. At this time, the oscillating circuit 104 can operate in a resonant state, so that the atomizing sheet works as much as possible in a resonant state, and the spraying device has a good spraying effect.

The embodiment of the present application provides a frequency locking circuit, and the frequency locking circuit outputs a preset control frequency band. The control frequency controls the switching of the switching circuit, and when the switching circuit is turned on and off for each control frequency, detects the voltage drop value of the sampling circuit corresponding to each control frequency, and finally obtains the maximum voltage drop value of the sampling circuit, according to the maximum The voltage drop value acquires a corresponding control frequency, so that the controller can control the switching circuit to be turned on and off according to the control frequency, and the oscillation circuit is locked at the resonance frequency to maintain the resonance state. Thus, on the one hand, the embodiment saves the manual debugging link. The production cost is saved and the production efficiency is improved. On the other hand, the spray device with the frequency-locked circuit can have a better spray effect and improve the user experience.

Referring to FIG. 5, an embodiment of the present application further provides a method for controlling a frequency locking circuit. The method can be applied to the frequency locking circuit in the above embodiment, and the method includes:

Step 11. Control the on/off of the switch circuit according to a preset control frequency band, and detect a voltage drop value corresponding to the sampling circuit, and obtain a control frequency corresponding to the maximum voltage drop value;

Step 12: Locking controls the on/off of the switch circuit according to the obtained control frequency.

In the embodiment of the present application, the oscillating circuit, the switching circuit, and the sampling circuit may be the oscillating circuit 104, the switching circuit 101, and the sampling circuit 102 in the above embodiments, respectively. The method provided by the embodiment of the present application is executed by the controller 103 in the above embodiment.

Before performing the method, the range of the preset control frequency may be preset, and within the range of the preset control frequency, a plurality of control frequencies are selected, the preset control frequency band is [f ₀ (1-a%), f ₀ (1+a%)], where f ₀ refers to the resonant frequency of the oscillating circuit in the frequency-locked circuit, and a is an arbitrary parameter within a preset range. For example, if the range of the preset control frequency is set to [f ₀ (1-10%), f ₀ (1+10%)], then it can be determined based on the range that several control frequencies are respectively f ₀ (1-10%) ), f ₀ (1-10%)+a, f ₀ (1-10%)+2a,...,f ₀ (1+10%), where the size of a is based on f ₀ (1-10%) The magnitude of the difference from f ₀ (1+10%) and the number of control frequencies are determined; the size of f ₀ can be obtained according to the calculation formula in the above embodiment of the frequency-locked circuit.

It should be noted that although the range of the preset control frequency is controlled within the upper 10% range of f ₀ , those skilled in the art can understand that the range of the preset control frequency can also be controlled to other values of f ₀ . Within the scope.

After determining the preset control frequency band, detecting a voltage drop value of the sampling circuit 102 based on each control frequency in the preset control frequency band, and finally obtaining a maximum voltage drop value and a control frequency corresponding to the maximum voltage drop value. Specifically, as shown in FIG. 6, the process includes:

Step b: decreasing or increasing the first oscillation frequency according to a preset frequency difference to obtain a second oscillation frequency, and acquiring a second voltage drop value of the sampling circuit according to the second oscillation frequency; the preset frequency The difference can be considered as a setting, or it can be set by the system;

In some embodiments, as shown in FIG. 7, the process of acquiring the control frequency corresponding to the maximum voltage drop value of the sampling circuit 102 may further include:

Step 111: Sort the plurality of preset control frequencies according to a frequency size;

Step 112: According to the sorting, sequentially select a control frequency to control on/off of the switch circuit according to a sequence from small to large, and acquire the switch according to each selected control frequency. The voltage drop value of the sampling circuit;

Step 113: After obtaining the voltage drop values of all the sampling circuits according to the plurality of preset control frequencies, obtaining a maximum voltage drop value;

Step 114: Acquire a preset control frequency according to the maximum voltage drop value.

The above steps 111-114 are explained by way of example below. For example, if the range of the preset control frequency is preset to be [90%f ₀ , 110%f ₀ ], then several control frequencies can be determined based on the range to be 90% f ₀ , f ₀ , 110% f _{0 , respectively} . First, the control signal with the control frequency of 90%f ₀ is output, the switch circuit is controlled to be turned on and off, and the voltage drop value of the sampling circuit is detected as V1 according to the control frequency 90%f ₀ , and then the control signal with the control frequency f ₀ is output. The control switch circuit is turned on and off, and the voltage drop value of the sampling circuit is detected as V2 according to the control frequency f ₀ , and finally the control signal with the control frequency of 110% f ₀ is output, and the control switch circuit is turned on and off, and 110% according to the control frequency. f ₀ detects that the voltage drop of the sampling circuit is V3. By comparing the sizes of V1, V2, and V3, the maximum voltage drop value is obtained, for example, the maximum voltage drop value is V2. At this time, the control frequency f ₀ corresponding to V2 is the preset control frequency, and the switch can be controlled according to the control frequency f _{0 .} The circuit is turned on and off, and drives the LC oscillation circuit to oscillate. At this time, the LC oscillation circuit approaches the resonance state.

In some embodiments, the voltage drop value of the sampling circuit may also be detected multiple times based on each control frequency. For example, the control signal with the control frequency of 50% f ₀ is outputted five times in succession, and the voltage drop value of the sampling circuit is detected each time. Finally, the average value of 5 times is obtained, which is the voltage drop value of the sampling circuit when the control frequency is 50%f ₀ .

The embodiment of the present application provides a method for controlling a frequency locking circuit, which detects a sampling circuit The voltage drop value obtains its corresponding control frequency, and the resonant frequency of the oscillating circuit can be automatically locked according to the acquired control frequency, thereby causing the oscillating circuit to operate in a resonant state. The method saves the manual debugging link in production, saves the generation cost and improves the production efficiency.

The above description is only the embodiment of the present application, and thus does not limit the scope of the patent application, and the equivalent structure or equivalent process transformation of the specification and the drawings of the present application, or directly or indirectly applied to other related technologies. The fields are all included in the scope of patent protection of this application.

Claims

A frequency locking circuit, characterized in that: the frequency locking circuit comprises: a switching circuit, a sampling circuit, a controller and an oscillating circuit,

An input end of the switch circuit is connected to the oscillating circuit, an output end of the switch circuit is connected to a first end of the sampling circuit, and a control signal output end of the controller is connected to a control end of the switch circuit, The detection signal input end of the controller is respectively connected to the output end of the switch circuit and the first end of the sampling circuit, and the second end of the sampling circuit is grounded;

The controller is configured to: control the on/off of the switch circuit according to a preset control frequency band, and detect a voltage drop value corresponding to the sampling circuit, obtain a control frequency corresponding to the maximum voltage drop value, and lock the acquired The control frequency controls on and off of the switching circuit.
The frequency locking circuit of claim 1 wherein said sampling circuit is a sampling resistor.
The frequency locking circuit according to claim 1, wherein the switching circuit comprises: a first resistor, a second resistor, and a switch tube;

One end of the first resistor is connected to a control signal output end of the controller, and the other end of the first resistor is respectively connected to one end of the second resistor and a control end of the switch tube; the input of the switch tube The end is connected to the oscillating circuit, and the output end of the switch tube is respectively connected to the first end of the sampling circuit and the detection signal input end of the controller; the other end of the second resistor is grounded.
The frequency-locking circuit according to claim 1, wherein the oscillating circuit comprises: a first inductor, a second inductor, a first capacitor, a second capacitor, and an atomizing sheet;

One end of the first inductor is connected to the power source, and the other end of the first inductor is respectively connected to one end of the first capacitor and an input end of the switch circuit; the other end of the first capacitor is respectively connected to the second inductor And a second capacitor;

One end of the atomization piece is connected to the second inductor, and the other end is connected to the second capacitor and grounded.
The frequency locking circuit according to claim 3, further comprising a filter circuit, the filter circuit comprising: a third resistor and a third capacitor;

One end of the third resistor is respectively connected to the first end of the sampling circuit and the output end of the switch tube, and the other end of the third resistor is connected to one end of the third capacitor and a detection signal of the controller An input end; the other end of the third capacitor is grounded.
A method for controlling a frequency-locked circuit, wherein the frequency-locking circuit is the frequency-locking circuit according to any one of claims 1 to 5, the method comprising:

Controlling the on/off of the switch circuit according to a preset control frequency band, and detecting a voltage drop value corresponding to the sampling circuit, and obtaining a control frequency corresponding to the maximum voltage drop value;

The lock controls the on and off of the switch circuit according to the acquired control frequency.
The method according to claim 6, wherein the controlling the on/off of the switch circuit according to a preset control frequency band, and detecting the voltage drop value corresponding to the sampling circuit, and obtaining the control corresponding to the maximum voltage drop value Frequency, including:

Step a, outputting a first oscillation frequency to the switch circuit in a preset control frequency band, and acquiring a first voltage drop value of the sampling circuit according to the first oscillation frequency, and saving the first oscillation frequency and the First pressure drop value;

Step b: decreasing or increasing the first oscillation frequency according to a preset frequency difference to obtain a second oscillation frequency, and acquiring a second voltage drop value of the sampling circuit according to the second oscillation frequency;

Step c, determining whether the second voltage drop value is greater than the first voltage drop value, and if so, replacing the second oscillation frequency and the second voltage drop value with the saved first oscillation frequency and the first The voltage drop value is obtained until the preset control frequency band is obtained such that the sampling circuit generates a control frequency corresponding to the maximum voltage drop value.
The method according to claim 6 or 7, wherein the preset control frequency band is [f 0 (1-a%), f 0 (1+a%)], wherein f 0 refers to The resonant frequency of the oscillating circuit in the frequency locking circuit, a is an arbitrary parameter within a preset range.