Coil radiation magnetic field shielding method based on active control

Abstract

A coil radiation magnetic field shielding method based on active control relates to the technical field of magnetic field shielding and mainly comprises the steps of shielding coil design, decoupling design of a shielding coil and a transmission coil, active control of radiation magnetic field shielding and the like. Meanwhile, switching control and resonance compensation are performed on a current loop of the shielding coil, so that the influence on the output power and the transmission efficiency of the system can be reduced as much as possible while active shielding control on a radiation magnetic field in a target area can be realized. The method can effectively simplify the system structure of coil radiation magnetic field shielding, and obtains a better shielding effect.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic field shielding, and in particular to a coil radiation magnetic field shielding method based on active control. Background Art

[0002] Magnetic field coupling wireless power transmission technology refers to the technology of transmitting energy through magnetic coupling by passing high-frequency AC power to the coupling coils, so that high-frequency alternating magnetic fields are generated between the coils. It is widely used in many aspects of daily life and industrial manufacturing due to its advantages of reliability, safety, and high flexibility. However, during the power transmission process, part of the magnetic field will spread to the surrounding non-working areas and cannot be effectively coupled, which will not only reduce the transmission efficiency of the system, but the excessive magnetic field radiation will also interfere with other circuit components and even cause damage.

[0003] At present, the main method for shielding the radiated magnetic field of wireless power transmission systems is to use high magnetic permeability materials to form a low magnetic resistance loop, or to use the eddy current reverse magnetic field induced by non-ferromagnetic materials to achieve a shielding effect. The restraining effect of magnetic materials on the radiated magnetic field is very limited, and aluminum plates are usually required to enhance the shielding effect. However, the use of aluminum plates will greatly reduce the degree of coupling between the transmission coils, and for some special equipment with limited volume, there is a problem of difficulty in installation. Summary of the invention

[0004] The present disclosure provides a more flexible and volume-saving coil radiation magnetic field shielding method based on active control, which utilizes the outer coil of the transmission coil as a shielding coil to generate a reverse magnetic field with a phase opposite to the source magnetic field, and performs switch control and resonance compensation on the current loop of the shielding coil, so that it can achieve active shielding control of the radiation magnetic field of the target area while minimizing the impact on the system output power and transmission efficiency.

[0005] Specifically, the process mainly includes the following steps:

[0006] S1, the outer coil of the transmission coil is led out as a magnetic field shielding coil to generate a reverse magnetic field with a phase opposite to the source magnetic field;

[0007] S2, decoupling the shielding coil and the transmission coil through resonance compensation;

[0008] S3, switches the current loop of the shielding coil to achieve active control of the magnetic field shielding strength.

[0009] Furthermore, the step S1 specifically includes:

[0010] Assuming that the input and output terminals of the transmission coil are terminals A and B, and the terminal of the outer shielding coil is C, the BC segment coil constitutes a magnetic field shielding coil, and its current direction is opposite to that of the AB segment coil of the power transmission coil, generating an anti-phase magnetic field to shield the radiation magnetic field of the power transmission coil;

[0011] The secondary coil is the same.

[0012] Furthermore, in step S1:

[0013] The current of the BC segment shielding coil is obtained from the power transmission current loop, that is, the current flowing into the A terminal and the current flowing into the C terminal are from the current output end of the same power supply, without adding a new power supply for the outer shielding coil.

[0014] Furthermore, the specific method of step S2 includes:

[0015] Resonant capacitors C3 and C4 are respectively set on the primary side of the system for the transmission coil and the shielding coil, and resonant capacitors C5 and C6 are respectively set on the secondary side of the system for the transmission coil and the shielding coil to form a resonant compensation structure to decouple the coupling relationship between the coils;

[0016] Among them, the resonance compensation calculation relationship is as follows:

[0017]

[0018] Where ω is the angular frequency; M2 is the self-inductance of the primary transmission coil L p The self-inductance L of the primary shielding coil p0 The mutual inductance of M3 is the self-inductance of the secondary transmission coil L s and the secondary shielding coil self-inductance L s0 of mutual induction.

[0019] Furthermore, the flow rate is calculated according to the following formula:

[0020] A power switch device is arranged on the current path flowing to the shielding coil to control the current loop of the shielding coil;

[0021] Active control of the magnetic field shielding strength is achieved by controlling the duty ratio of the PWM wave input to the primary power switch device and the secondary power switch device.

[0022] Furthermore, the power switch device adopts a MOS tube.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) The outer coil of the transmission coil of the wireless power transmission system is used as a shielding coil to generate a magnetic field with a phase opposite to the source magnetic field, thereby shielding the radiation magnetic field of the transmission coil and simplifying the shielding system structure;

[0025] (2) The current of the shielding coil is obtained from the power transmission current loop, and there is no need to add a power supply for the outer shielding coil, which further simplifies the shielding system structure; at the same time, since the power transmission coil and the outer shielding coil use the same power supply, the power transmission loop current has the same frequency as the outer magnetic field shielding coil loop current, which can achieve a better magnetic field shielding effect;

[0026] (3) By designing a resonant compensation network to decouple the shielding coil and the power transmission coil, the shielding effect on the target area is improved, and the problem that the shielding coil of the active shielding method will affect the equivalent magnetic coupling of the original system is solved;

[0027] (4) By controlling the power switch device of the shielding coil current loop, the system magnetic field shielding strength can be actively controlled, so that it can actively shield the magnetic field radiated by the transmission coil while minimizing the impact on the system transmission efficiency and output power. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present disclosure.

[0029] Figure 1 is a schematic diagram of an exemplary primary coil;

[0030] Figure 2 is a schematic diagram of an overall circuit of a system according to an exemplary embodiment of the present disclosure;

[0031] Figure 3 An equivalent circuit of the transmission coil and the shielding coil decoupling of an exemplary embodiment. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0033] The present disclosure provides a coil radiation magnetic field shielding method based on active control, which is mainly completed through three parts: shielding coil design, decoupling design of shielding coil and transmission coil, and active control of radiation magnetic field shielding.

[0034] In an exemplary embodiment, the specific process is as follows:

[0035] 1. Design of transmission coil magnetic field shielding coil

[0036] like Figure 1 As shown in the schematic diagram of the primary coil, in order to shield the radiated magnetic field of the transmission coil of the wireless power transmission system, the outer coil of the transmission coil is led out as a magnetic field shielding coil. Terminals A and B are the input and output terminals of the transmission coil, and C is the lead-out terminal of the outer shielding coil. The AB segment coil serves as a power transmission coil, and the current flows in a counterclockwise direction. The BC segment coil serves as a magnetic field shielding coil, and the current flows in a clockwise direction, which is exactly opposite to the current direction of the power transmission coil, generating an anti-phase magnetic field that can shield the radiated magnetic field of the power transmission coil. The secondary coil is the same.

[0037] like Figure 2 As shown in the circuit schematic, in order to simplify the system structure of active shielding, the current of the BC segment shielding coil is obtained from the power transmission current loop, without adding a power supply for the outer shielding coil. In addition, since the power transmission coil and the outer shielding coil use the same power supply, the power transmission loop current has the same frequency as the outer magnetic field shielding coil loop current, so this method can achieve a better magnetic field shielding effect.

[0038] 2. Decoupling of shielding coil and transmission coil

[0039] Because the outer magnetic field shielding coil and the system power transmission coil are taken from the same coil, there will be a coupling relationship between them. Figure 2 and Figure 3 As shown in the circuit schematic, the coils are decoupled and equivalently transformed, and capacitors C3 and C4 are added to the primary side of the system, and capacitors C5 and C6 are added to the secondary side of the system to form a resonant compensation structure to decouple the coupling relationship between the coils.

[0040] The resonance compensation calculation formula is as follows:

[0041]

[0042] By decoupling the shielding coil and the transmission coil and designing a resonant compensation network, the magnetic field shielding effect can be effectively improved. At the same time, the problem that the shielding coil of the active shielding method will affect the equivalent magnetic coupling of the original transmission system is solved.

[0043] 3. Active control of radiation magnetic field shielding

[0044] like Figure 2 As shown, a power switch device is used to control the current loop of the outer magnetic field shielding coil, and the active control of the magnetic field shielding strength is achieved by controlling the duty cycle of the PWM wave input to the primary MOS tube S1 and the secondary MOS tube S2.

[0045] By actively controlling the intensity of the magnetic field shielding, the magnetic field radiated by the transmission coil can be effectively shielded while minimizing the impact of the shielding coil loop on the system output power and transmission efficiency.

[0046] In this embodiment, the outer coil of the transmission coil is used to generate a magnetic field with a phase opposite to that of the source magnetic field; the shielding coil and the transmission coil are decoupled, and a resonant compensation network is designed to improve the shielding effect; the power switch device of the shielding coil current loop is controlled to actively adjust the system magnetic field shielding strength. This method can be widely used in coil radiation magnetic field shielding in technical fields such as wireless power transmission, aerospace / space system energy conversion and control, and power electronics.

[0047] The above technical scheme is only an exemplary embodiment of the present invention. For those skilled in the art, it is easy to make various types of improvements or modifications based on the application methods and principles disclosed in the present invention, and it is not limited to the method described in the above specific embodiment of the present invention. Therefore, the method described above is only preferred and does not have a restrictive meaning.

Claims

1. A method for shielding a coil radiation magnetic field based on active control, comprising the following steps: S1, the outer coil of the transmission coil is led out as a magnetic field shielding coil to generate a reverse magnetic field with a phase opposite to the source magnetic field; S2, decoupling the shielding coil and the transmission coil through resonance compensation; S3, switches the current loop of the shielding coil to achieve active control of the magnetic field shielding strength.

2. The method according to claim 1, characterized in that: The step S1 specifically includes: Assuming that the input and output terminals of the transmission coil are terminals A and B, and the terminal of the outer shielding coil is C, the BC segment coil constitutes a magnetic field shielding coil, and its current direction is opposite to that of the AB segment coil of the power transmission coil, generating an anti-phase magnetic field to shield the radiation magnetic field of the power transmission coil; The secondary coil is the same.

3. The method according to claim 2, characterized in that In step S1: The current of the BC segment shielding coil is obtained from the power transmission current loop, that is, the current flowing into the A terminal and the current flowing into the C terminal are from the current output end of the same power supply, without adding a new power supply for the outer shielding coil.

4. The method according to claim 2 or 3, characterized in that: The specific method of step S2 includes: Resonant capacitors C3 and C4 are respectively set on the primary side of the system for the transmission coil and the shielding coil, and resonant capacitors C5 and C6 are respectively set on the secondary side of the system for the transmission coil and the shielding coil to form a resonant compensation structure to decouple the coupling relationship between the coils; Among them, the resonance compensation calculation relationship is as follows: Where ω is the angular frequency; M2 is the self-inductance of the primary transmission coil L p The self-inductance L of the primary shielding coil p0 The mutual inductance of M3 is the self-inductance of the secondary transmission coil L s and the secondary shielding coil self-inductance L s0 of mutual induction.

5. The method according to claim 1, characterized in that The flow rate is calculated according to the following formula: A power switch device is arranged on the current path flowing to the shielding coil to control the current loop of the shielding coil; Active control of the magnetic field shielding strength is achieved by controlling the duty ratio of the PWM wave input to the primary power switch device and the secondary power switch device.

6. The method according to claim 5, characterized in that The power switch device adopts a MOS tube.

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