An ultrasonic power supply impedance network, variable inductance, control circuit and control method

Abstract

This invention discloses an ultrasonic power supply impedance network, a variable inductor, a control circuit, and a control method, including a variable inductor, an ultrasonic power supply impedance network, and a control circuit. The variable inductor consists of a main magnetic core, two auxiliary magnetic cores, a main winding, and auxiliary windings, with an air gap between the auxiliary magnetic cores and the main magnetic core. By adjusting the control current, the magnetic saturation level of the auxiliary magnetic cores is changed, thereby changing the magnetic saturation state of the main magnetic core, achieving dynamic change of the inductance value. The ultrasonic power supply load is capacitive, and the control circuit can make the load impedance and the variable inductor reach a resonant state, effectively reducing losses and improving energy transmission efficiency. Furthermore, the impedance matching method of this invention utilizes two auxiliary inductors, improving the impedance matching speed through coarse adjustment and improving the impedance matching accuracy through fine adjustment. It has advantages such as high matching accuracy, wide matching range, and dynamic adjustment, further expanding the application field of variable inductors.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic control and impedance matching, and in particular to an ultrasonic power supply impedance network, a variable inductor, a control circuit, and a control method. Background Technology

[0002] Ultrasonic power supplies, as important electronic devices, have been widely used in underwater sonar, medical and health, aerospace, and industrial production. The operating conditions of ultrasonic power supplies are harsh, and they are susceptible to temperature drift, which significantly alters their capacitive load characteristics. To ensure the ultrasonic power supply operates in a resonant state and achieves maximum power output on the load side, traditional ultrasonic power supplies typically employ impedance matching and frequency tracking of the load's output voltage and current. However, this approach suffers from poor impedance matching accuracy, slow response speed, small matching range, and poor frequency tracking accuracy. Existing solutions are insufficient for applying ultrasonic power supplies in even more demanding operating conditions.

[0003] Therefore, how to provide a solution to the above problems is a problem that needs to be solved by those skilled in the art. Summary of the Invention

[0004] This invention discloses an ultrasonic power supply impedance network, a variable inductor, a control circuit, and a control method. The ultrasonic power supply impedance matching and control method based on a variable inductor, by adding a variable inductor to the ultrasonic power supply impedance network, makes the series branch of the ultrasonic power supply impedance network resonant. When the ultrasonic power supply is in operation, the ultrasonic power supply impedance network changes with temperature. The control circuit controls the inductance value of the variable inductor to keep the series branch of the ultrasonic power supply impedance network in a resonant state. Existing ultrasonic power supply impedance matching methods have poor dynamic performance, low matching accuracy, and small matching range. Compared with existing ultrasonic power supply impedance matching methods, the ultrasonic power supply impedance matching method based on a variable inductor uses two auxiliary inductors to improve the matching speed of the variable inductor through coarse adjustment and improve the matching accuracy through fine adjustment. It has advantages such as fast matching response speed, high matching accuracy, wide matching range, reduced ultrasonic power supply loss, and maximum power transmission. The invention also discloses an ultrasonic power supply impedance matching control circuit and control method based on a variable inductor, expanding the application fields of variable inductors.

[0005] To address the aforementioned technical problems, the present invention adopts the following technical solution:

[0006] The ultrasonic power supply impedance network includes: the static equivalent capacitance C of the ultrasonic power supply. O The dynamic equivalent capacitance C of the ultrasonic power supply m The dynamic equivalent inductance L of the ultrasonic power supply mThe dynamic equivalent resistance R of the ultrasonic power supply m The equivalent impedance of the ultrasonic power supply impedance network is:

[0007]

[0008] This can be further simplified to the resistive component as:

[0009]

[0010] The reactance component is:

[0011]

[0012] Where ω is the angular frequency of the ultrasonic power supply impedance network.

[0013] The variable inductor for the ultrasonic power supply impedance matching network includes: two auxiliary magnetic cores M1 and M2 and a main magnetic core M. Auxiliary windings are wound on the auxiliary magnetic cores M1 and M2, and a main winding is wound on the main magnetic core M. An air gap is formed between the upper end of the auxiliary magnetic core M1 and the left end of the main magnetic core M, and an air gap is formed between the upper end of the auxiliary magnetic core M2 and the right end of the main magnetic core M. A DC bias current source is used. A DC bias current source B ;

[0014] The auxiliary winding of the auxiliary magnetic core M1 is the first winding, and the number of turns of the first winding is N. M1 ;

[0015] The first end of the first winding is connected to the DC current source DC A The positive terminal connection;

[0016] The second end of the first winding is connected to the DC current source DC. A The negative terminal connection;

[0017] The auxiliary winding of the auxiliary magnetic core M2 is the second winding, and the number of turns of the second winding is N. M2 ;

[0018] The first end of the second winding is connected to the DC current source DC. B The positive terminal connection;

[0019] The second end of the second winding is connected to the DC current source DC. B The negative terminal connection;

[0020] The main winding of the main magnetic core M is the third winding, and the number of turns of the third winding is N. M .

[0021] Among them, the auxiliary magnetic core M1 is relatively long and has a greater impact on the variable inductance value of the main magnetic core M. It is mainly used for coarse adjustment of the variable inductance value of the main magnetic core M. The auxiliary magnetic core M2 is relatively short and has a smaller impact on the variable inductance value of the main magnetic core M. It is mainly used for fine adjustment of the variable inductance value of the main magnetic core M. The variable inductance value of the main magnetic core M can be calculated by the following formula:

[0022]

[0023] μ′ M =μ M +k1I M1 +k2I M2

[0024] Further simplification of the above equation yields:

[0025]

[0026] When the auxiliary magnetic core M1 is coarsely adjusted for variable inductance, the current value is calculated using the following formula:

[0027]

[0028] When the auxiliary magnetic core M2 is finely adjusted with variable inductance, the current value is calculated using the following formula:

[0029]

[0030] The control circuit for ultrasonic power supply impedance network matching based on variable inductance includes:

[0031] Current sensor, voltage sensor, current phase detection circuit, voltage phase detection circuit, phase comparator, TMS320F28335 digital signal processor, PWM module P1, PWM module P2, drive circuit Q1, drive circuit Q2, current control circuit C1, current control circuit C2.

[0032] Optionally, the control method based on the impedance matching of the ultrasonic power supply network with variable inductance is as follows:

[0033] Step 1: The current sensor collects the current of the series branch of the ultrasonic power supply impedance network, and the voltage sensor collects the voltage of the series branch of the ultrasonic power supply impedance network.

[0034] Step 2: The current sensor sends the collected current of the series branch of the ultrasonic power supply impedance network to the current phase detection circuit, and the voltage sensor sends the collected voltage of the series branch of the ultrasonic power supply impedance network to the voltage phase detection circuit.

[0035] Step 3: The current phase detection circuit outputs current phase α, which is sent to the phase comparator; the voltage phase detection circuit outputs voltage phase β, which is sent to the phase comparator.

[0036] Step 4: The phase difference θ output by the phase comparator is sent to the TMS320F28335 digital signal processor;

[0037] Step 5: The TMS320F28335 digital signal processor starts the control program to control the PWM module P1 to output a drive signal with the corresponding duty cycle and send it to the drive circuit Q1. The TMS320F28335 digital signal processor starts the control program to control the PWM module P2 to output a drive signal with the corresponding duty cycle and send it to the drive circuit Q2.

[0038] Step 6: Drive circuit Q1 drives current control circuit C1 adjusts DC bias current source DC A The magnitude of the output current is determined by the drive circuit Q2 and the drive current control circuit C2, which adjusts the DC bias current source DC. B The magnitude of the output current;

[0039] The inductance value L of a variable inductor VI The impedance changes with the control current, ensuring that the series branch of the ultrasonic power supply impedance network remains in a resonant state. At this point, the equivalent impedance of the ultrasonic power supply impedance network is:

[0040]

[0041] Further simplification yields the resistance component as:

[0042]

[0043] The reactance component is:

[0044]

[0045] When the ultrasonic power supply impedance network reaches a resonant state, that is, when the ultrasonic power supply impedance network is purely resistive, the inductance value of the variable inductor is:

[0046]

[0047]

[0048] Where ω is the series resonant angular frequency of the ultrasonic power supply impedance network.

[0049] As can be seen from the above technical methods, the embodiments of the present invention have the following beneficial effects:

[0050] This invention discloses an ultrasonic power supply impedance network, a variable inductor, a control circuit, and a control method. The method, based on a variable inductor for ultrasonic power supply impedance matching and control, incorporates a variable inductor into the ultrasonic power supply impedance network, ensuring the series branch of the network is in a resonant state. When the ultrasonic power supply is in operation, the impedance network fluctuates with temperature changes. The control circuit adjusts the inductance value of the variable inductor to maintain the resonant state of the series branch. The variable inductor-based ultrasonic power supply impedance matching method uses two auxiliary inductors. Coarse adjustment improves the matching speed of the variable inductor, while fine adjustment improves its accuracy. It offers advantages such as fast impedance matching response, high matching accuracy, wide matching range, reduced ultrasonic power supply loss, and maximum power transmission. The invention also discloses a control circuit and method for ultrasonic power supply impedance matching based on a variable inductor, expanding the application areas of variable inductors. Attached Figure Description

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This is a schematic diagram of the ultrasonic power supply impedance matching and control circuit based on variable inductance of the present invention.

[0053] Figure 2 This is a schematic diagram of the variable inductor structure of the present invention;

[0054] Figure 3 This is a schematic diagram of the control program flow of the TMS320F28335 digital signal processor of the present invention;

[0055] Figure 4 This is a schematic diagram of the ultrasonic power supply impedance matching control process based on variable inductor according to the present invention. Detailed Implementation

[0056] To make the objectives, technical solutions, and features of the embodiments of the present invention clearer, 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.

[0057] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the ultrasonic power supply impedance matching and control circuit based on variable inductance according to the present invention. The ultrasonic power supply impedance network includes: the static equivalent capacitance C of the ultrasonic power supply. O The dynamic equivalent capacitance C of the ultrasonic power supply m The dynamic equivalent inductance L of the ultrasonic power supply m The dynamic equivalent resistance R of the ultrasonic power supply m The specific structure is as follows: the dynamic equivalent capacitance C of the ultrasonic power supply. m The dynamic equivalent inductance L of the ultrasonic power supply m The dynamic equivalent resistance R of the ultrasonic power supply m The static equivalent capacitance C of the ultrasonic power supply is connected in series. O Parallel connection; the equivalent impedance of the ultrasonic power supply impedance network is:

[0058]

[0059] This can be further simplified to the resistive component as:

[0060]

[0061] The reactance component is:

[0062]

[0063] Where ω is the angular frequency of the ultrasonic power supply impedance network.

[0064] The control circuit based on the ultrasonic power supply impedance network matching of variable inductance includes: a current sensor, a voltage sensor, a current phase detection circuit, a voltage phase detection circuit, a phase comparator, a TMS320F28335 digital signal processor, PWM module P1, PWM module P2, drive circuit Q1, drive circuit Q2, current control circuit C1, and current control circuit C2.

[0065] Please refer to Figure 2 , Figure 2 This is a schematic diagram of the variable inductor structure for ultrasonic power supply impedance network matching of the present invention, including: two auxiliary magnetic cores M1 and M2 and a main magnetic core M. Auxiliary windings are wound on the auxiliary magnetic cores M1 and M2, and a main winding is wound on the main magnetic core M. An air gap is formed between the upper end of the auxiliary magnetic core M1 and the left end of the main magnetic core M, and an air gap is formed between the upper end of the auxiliary magnetic core M2 and the right end of the main magnetic core M. A DC bias current source is also included. A DC bias current source B .

[0066] The auxiliary winding of the auxiliary magnetic core M1 is the first winding, and the number of turns of the first winding is N. M1 ;

[0067] The first end of the first winding is connected to the DC current source DC A The positive terminal connection;

[0068] The second end of the first winding is connected to the DC current source DC. A The negative terminal connection;

[0069] The auxiliary winding of the auxiliary magnetic core M2 is the second winding, and the number of turns of the second winding is N. M2 ;

[0070] The first end of the second winding is connected to the DC current source DC. B The positive terminal connection;

[0071] The second end of the second winding is connected to the DC current source DC. B The negative terminal connection;

[0072] The main winding of the main magnetic core M is the third winding, and the number of turns of the third winding is N. M .

[0073] Among them, the auxiliary magnetic core M1 is relatively long and has a greater impact on the variable inductance value of the main magnetic core M. It is mainly used for coarse adjustment of the variable inductance value of the main magnetic core M. The auxiliary magnetic core M2 is relatively short and has a smaller impact on the variable inductance value of the main magnetic core M. It is mainly used for fine adjustment of the variable inductance value of the main magnetic core M. The variable inductance value of the main magnetic core M can be calculated by the following formula:

[0074]

[0075] μ′ M =μ M +k1I M1 +k2I M2

[0076] Further simplification of the above equation yields:

[0077]

[0078] When the auxiliary magnetic core M1 is coarsely adjusted for variable inductance, the current value is calculated using the following formula:

[0079]

[0080] When the auxiliary magnetic core M2 is finely adjusted with variable inductance, the current value is calculated using the following formula:

[0081]

[0082] The magnetic saturation of the main magnetic core M is influenced by the DC bias current source on the two auxiliary magnetic cores M1 and M2. A DC BThe value of the variable inductance L on the main magnetic core changes due to the control of the variable inductance. VI It can be continuously adjusted. The auxiliary inductor M1 improves the matching speed of the variable inductor through coarse adjustment, and the auxiliary inductor M2 improves the matching accuracy of the variable inductor through fine adjustment. It has the advantages of fast impedance matching response speed, high matching accuracy and a wide range of variable inductance value adjustment.

[0083] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the control program flow of the TMS320F28335 digital signal processor of the present invention. After receiving the phase difference between the current and voltage of the series branch in the ultrasonic power supply impedance network calculated by the phase comparator, the TMS320F28335 digital signal processor compares it with the reference phase θ. ref The error is obtained by subtracting 0 from the value of 0, and then the corresponding duty cycle drive signal is generated by the PID program, limiter and PWM module.

[0084] Please refer to Figure 4 , Figure 4 This is a schematic diagram of the ultrasonic power supply impedance matching control process based on variable inductance of the present invention. A current sensor collects the current in the series branch of the ultrasonic power supply impedance network, and a voltage sensor collects the voltage in the series branch of the ultrasonic power supply impedance network. The current sensor sends the collected current to a current phase detection circuit to detect the current phase as α, and the voltage sensor sends the collected voltage to a voltage phase detection circuit to detect the voltage phase as β. The current phase α and the voltage phase β are compared by a phase comparator to obtain the phase difference θ, specifically using the following formula:

[0085] θ=α-β

[0086] After logically determining whether θ equals zero, if θ equals zero, it indicates that the ultrasonic power supply impedance network has reached a resonant state, meaning the ultrasonic power supply impedance network is purely resistive, and the process returns directly, exiting the next step of the control flow. If θ does not equal zero, the TMS320F28335 digital signal processor starts the control program, calling the PWM module to output a drive signal with the corresponding duty cycle to the drive circuit. The drive circuit drives the current control circuit to control the output current of the DC bias current source. Through the coarse and fine adjustments of the auxiliary magnetic cores M1 and M2, the variable inductance value is matched with the ultrasonic power supply impedance network, meaning that the series branch of the ultrasonic power supply impedance network always maintains a resonant state. At this time, the equivalent impedance of the ultrasonic power supply impedance network is:

[0087]

[0088] Further simplification yields the resistance component as:

[0089]

[0090] The reactance component is:

[0091]

[0092] When the series branch of the ultrasonic power supply impedance network reaches resonance, that is, the ultrasonic power supply impedance network is purely resistive, the inductance value of the variable inductor is:

[0093]

[0094]

[0095] Where ω is the series resonant angular frequency of the ultrasonic power supply impedance network.

[0096] In summary, this invention discloses an ultrasonic power supply impedance network, a variable inductor, a control circuit, and a control method. Traditional ultrasonic power supply impedance matching methods suffer from poor matching accuracy, slow response speed, and small matching range, making it difficult to adapt to the rapid changes in load impedance caused by temperature drift during ultrasonic power supply operation. The ultrasonic power supply impedance matching based on a variable inductor, by introducing a variable inductor and combining it with a control circuit and method, ensures that the ultrasonic power supply impedance maintains its series branch in a resonant state regardless of changes in the ultrasonic power supply load. The variable inductor-based ultrasonic power supply impedance matching method uses two auxiliary inductors to improve the matching speed through coarse adjustment and improve the matching accuracy through fine adjustment. It has advantages such as fast impedance matching response speed, high matching accuracy, wide matching range, reduced ultrasonic power supply loss, and maximum power transmission. Simultaneously, the invention discloses a control circuit and method for ultrasonic power supply impedance matching based on a variable inductor, expanding the application areas of variable inductors.

[0097] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the elements or modules referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as implying or indicating relative importance.

[0098] Unless otherwise explicitly specified and limited, the terms "connection" and "installation" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or a simple link through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0099] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; the description of the embodiments disclosed in this invention enables those skilled in the art to use or implement this invention, and they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these substitutions or modifications do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the application.

Claims

1. An ultrasonic power supply impedance matching system, characterized in that, include: A variable inductor is used to match the impedance network of the ultrasonic power supply, which includes the static equivalent capacitance of the ultrasonic power supply. C O Dynamic equivalent capacitance of ultrasonic power supply C m Dynamic equivalent inductance of ultrasonic power supply L m The dynamic equivalent resistance of the ultrasonic power supply R m ; The variable inductor includes: Two auxiliary magnetic cores M1, M2 and a main magnetic core M, auxiliary magnetic cores M1 and M2 are wound with auxiliary windings, the main magnetic core M is wound with a main winding, the upper end of the auxiliary magnetic core M1 is opened with an air gap from the left end of the main magnetic core M, the upper end of the auxiliary magnetic core M2 is opened with an air gap from the right end of the main magnetic core M, a direct current bias current source DC A , a direct current bias current source DC B ; The auxiliary winding of the auxiliary magnetic core M1 is the first winding, and the number of turns of the first winding is... N M1 ; The first end of the first winding is connected to the DC bias current source DC A The positive terminal connection; The second end of the first winding is connected to the DC bias current source DC A The negative terminal connection; The auxiliary winding of the auxiliary magnetic core M2 is the second winding, and the number of turns of the second winding is... N M2 ; The first end of the second winding is connected to the DC bias current source DC B The positive terminal connection; The second end of the second winding is connected to the DC bias current source DC B The negative terminal connection; The main winding of the main magnetic core M is the third winding, and the number of turns of the third winding is... N M ; The auxiliary magnetic core M1 is used for coarse adjustment of the variable inductance value of the main magnetic core M, and the auxiliary magnetic core M2 is used for fine adjustment of the variable inductance value of the main magnetic core M. The magnetic saturation of the main magnetic core M is controlled by the DC bias current source on both auxiliary magnetic cores, which changes the variable inductance value. L VI The dynamic equivalent capacitance of the ultrasonic power supply in the series branch of the ultrasonic power supply impedance network, after adding a variable inductor, can continuously change. C m Dynamic equivalent inductance of ultrasonic power supply L m Resonance is generated; When the ultrasonic power supply impedance network reaches a resonant state, that is, when the ultrasonic power supply impedance network is purely resistive, the inductance value of the variable inductor is: in, ω This is the series resonant angular frequency of the ultrasonic power supply impedance network. The control circuit, used to control the variable inductor, includes: a current sensor, a voltage sensor, a current phase detection circuit, a voltage phase detection circuit, a phase comparator, a TMS320F28335 digital signal processor, a PWM module P1, a PWM module P2, a drive circuit Q1, a drive circuit Q2, a current control circuit C1, and a current control circuit C2. The input terminal of the current sensor is connected to the ultrasonic power supply impedance matching network. C m , L m and R m In the circuit, the output of the current sensor is connected to the input of the current phase detection circuit, the output of the current phase detection circuit is connected to the first input of the phase comparator, and the input of the voltage sensor is connected to the ultrasonic power supply impedance matching network. C m , L m and R m In the circuit, the output of the voltage sensor is connected to the input of the voltage phase detection circuit, the output of the voltage phase detection circuit is connected to the second input of the phase comparator, the output of the phase comparator is connected to the input of the TMS320F28335 digital signal processor, the first output of the TMS320F28335 digital signal processor is connected to the input of the PWM module P1, the output of the PWM module P1 is connected to the input of the drive circuit Q1, the output of the drive circuit Q1 is connected to the input of the current control circuit C1, and the output of the current control circuit C1 is connected to the DC bias current source DC. A In the circuit, the second output terminal of the TMS320F28335 digital signal processor is connected to the input terminal of the PWM module P2, the output terminal of the PWM module P2 is connected to the input terminal of the drive circuit Q2, the output terminal of the drive circuit Q2 is connected to the input terminal of the current control circuit C2, and the output terminal of the current control circuit C2 is connected to the DC bias current source DC. B In the circuit where it is located.

2. The ultrasonic power supply impedance matching system according to claim 1, characterized in that, The control method for the ultrasonic power supply impedance network matching control circuit includes the following steps: Step 1: The current sensor acquires the current of the series branch of the ultrasonic power supply impedance network, and the voltage sensor acquires the voltage of the series branch of the ultrasonic power supply impedance network. Step 2: The current sensor sends the collected ultrasonic power supply impedance network series branch current to the current phase detection circuit, and the voltage sensor sends the collected ultrasonic power supply impedance network series branch voltage to the voltage phase detection circuit. Step 3: The current phase detection circuit outputs the current phase. α The voltage phase is sent to the phase comparator, and the voltage phase detection circuit outputs the voltage phase. β The signal is sent to the phase comparator; Step 4: The phase comparator outputs the phase difference. θ The signal is sent to the TMS320F28335 digital signal processor. Step 5: The TMS320F28335 digital signal processor starts the control program to control the PWM module P1 to output a drive signal with a corresponding duty cycle to the drive circuit Q1, and the TMS320F28335 digital signal processor starts the control program to control the PWM module P2 to output a drive signal with a corresponding duty cycle to the drive circuit Q2. Step 6: The driving circuit Q1 drives the current control circuit C1 to adjust the DC bias current source DC. A The output current magnitude is determined by the driving circuit Q2, which drives the current control circuit C2 to adjust the DC bias current source DC. B The magnitude of the output current; At this time, the inductance value of the variable inductor L VI It changes with the change of control current, so that the series branch of the ultrasonic power supply impedance network always remains in a resonant state.

3. The ultrasonic power supply impedance matching system according to claim 1, further characterized in that, The variable inductance value of the main magnetic core M can be calculated using the following formula: Further simplification of the above equation yields: When the auxiliary magnetic core M1 is coarsely adjusted for variable inductance, the current value is calculated using the following formula: When the auxiliary magnetic core M2 is finely adjusted with variable inductance, the current value is calculated using the following formula: in, l M The length of the main magnetic core M; l g This is the air gap length; A M The cross-sectional area of ​​the main magnetic core M; μ' M The permeability of the main magnetic core M after being controlled by two auxiliary magnetic cores M1 and M2; μ o The air gap permeability; μ M The initial permeability of the main magnetic core M; k 1 represents the adjustment coefficient of the auxiliary magnetic core M1; k 2 represents the adjustment coefficient of the auxiliary magnetic core M2; I M1 DC bias current source A ; output current; I M2 DC bias current source B The output current.

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