Direct-current demagnetization circuit, demagnetization method adopting same and direct-current demagnetization device

Abstract

The invention provides a direct-current demagnetization circuit, a demagnetization method adopting the same and a direct-current demagnetization device. The direct-current demagnetization circuit comprises a power supply unit, a direct-current demagnetization unit, a switching unit and a resistance adjusting unit, wherein the power supply unit, the direct-current demagnetization unit, the switching unit and the resistance adjusting unit are sequentially connected in series to form a closed loop; according to the direct-current demagnetization circuit, demagnetization currents with alternately-changed polarities are applied to the two ends of a direct-current demagnetization unit, so that all residual magnetism of a to-be-demagnetized product is removed. The direct-current demagnetization circuit provided by the invention can recover the inductance value of a magnetic core prepared from a material with a high remanence characteristic after saturation to 90% or above of the inductance value before saturation.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic core demagnetization, and in particular relates to a direct current demagnetization circuit, a demagnetization method using the same, and a direct current demagnetization device. Background Art

[0002] Ferrite materials are widely used in circuits because of their high resistivity and low price, especially for high-frequency electronic device formulations. They can provide very high impedance values ​​above 10M, so they are used in high-frequency EMC filters. However, the remanence (Br) of the above-mentioned ferrite materials is relatively high, that is, when the magnetic core is saturated, there will be a high remanence, and the inductance of ferrite materials is positively correlated with the magnetic permeability. When ferrite materials are in a saturated state, their magnetic permeability will drop significantly. This is because the magnetic permeability μ is positively correlated with the slope on the BH curve, and the Br value of ferrite materials is higher after saturation, resulting in a smaller change in the B value under the same H change, thereby reducing the magnetic permeability, and ultimately causing the inductance value to drop (about 70% before saturation), causing the initial inductance of the ferrite material to be lower than the standard lower limit.

[0003] At present, the method disclosed in the prior art to remove Br from the magnetic core is to heat it to the Curie temperature and keep it warm for a period of time to achieve the demagnetization effect. In fact, the magnetic core is usually used in combination with other components (such as capacitors, PCB boards or potting components, etc.), and these components may not be able to withstand the high temperature of 160°C, so it is impossible to remove the Br of the product by directly heating the electronic components.

[0004] Therefore, in the art, there is an urgent need to develop a demagnetization method to solve the above problems. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a DC demagnetization circuit, a demagnetization method and a DC demagnetization device using the same. The DC demagnetization circuit provided by the present invention can restore the inductance of a magnetic core made of a material with high remanence (Br) characteristics to more than 90% of the inductance before saturation.

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a DC demagnetization circuit, the DC demagnetization circuit comprising a power supply unit, a DC demagnetization unit, a switching unit and a resistance adjustment unit, wherein the power supply unit, the DC demagnetization unit, the switching unit and the resistance adjustment unit are sequentially connected in series to form a closed loop;

[0008] The DC demagnetization circuit removes all residual magnetism of the product to be demagnetized by applying a demagnetization current with alternating polarity to both ends of the DC demagnetization unit.

[0009] Aiming at the technical problems that the inductance of the magnetic core made of high Br characteristic powder in the prior art will drop significantly after saturation, and for the magnetic core assembled in the module, if there are some components in the module that cannot be heated to the Curie temperature of the magnetic core, then the method of recovering the inductance of the magnetic core by directly heating to the Curie temperature will not be implemented, the present invention designs the composition of the DC demagnetization circuit so that an alternating magnetic field is formed on the DC demagnetization unit, especially a reverse magnetic field opposite to the original residual magnetism is applied, so as to completely eliminate the residual magnetism in the magnetic core component. This DC demagnetization circuit requires that the strength of the reverse magnetic field applied is sufficient to cover all magnetic domains of the product to be demagnetized, so as to ensure that each magnetic zone in the product can be fully demagnetized, thereby eliminating all residual magnetism, further improving the application range and demagnetization effect of the magnetic core demagnetization. In addition, the overall DC demagnetization circuit structure provided by the present invention is simple and practical, and can achieve demagnetization in just a few cycles with high speed and efficiency. At the same time, the DC demagnetization circuit provided by the present invention is easy to be used repeatedly in actual products, has no special requirements for product structure and function, and has strong applicability, thereby solving the technical problem that the existing demagnetization method requires the magnetic core to stop working or even cannot be directly operated in the product.

[0010] Preferably, the power supply unit comprises a direct current power supply.

[0011] Preferably, the DC demagnetization unit comprises a DC demagnetization coil.

[0012] Preferably, the switching unit comprises a switch element.

[0013] Preferably, the resistance adjusting unit comprises an adjustable resistor.

[0014] Preferably, one end of the DC demagnetization coil is connected to one end of the DC power supply, the other end of the DC demagnetization coil is connected to one end of the switching element, the other end of the switching element is connected to one end of the adjustable resistor, and the other end of the adjustable resistor is connected to the other end of the DC power supply.

[0015] Preferably, the output voltage range of the DC power supply is 12V to 48V, for example, 12V, 16V, 18V, 20V, 22V, 24V, 28V, 30V, 32V, 36V, 38V, 40V, 42V, 44V, 46V, 48V, etc. The DC demagnetization circuit provided by the present invention is inputted with a DC constant voltage output source, and compared with 220V AC, the input voltage of the present invention is lower, safer, and more stable.

[0016] Preferably, the number of turns of the DC demagnetization coil is 3 to 15 turns, for example, 3 turns, 5 turns, 8 turns, 10 turns, 12 turns, 15 turns, etc. The present invention further increases the magnetic field strength by adjusting the number of turns of the DC demagnetization coil.

[0017] Preferably, the inner diameter of the DC demagnetization coil is 3mm to 60mm, preferably 5mm to 8mm, for example, 3mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 10mm, 12mm, 15mm, 18mm, 20mm, 22mm, 25mm, 28mm, 30mm, 32mm, 35mm, 38mm, 40mm, 42mm, 45mm, 48mm, 50mm, 52mm, 55mm, 58mm, 60mm, etc. The present invention adjusts the inner diameter of the DC demagnetization coil so that the magnetic core to be demagnetized can be placed in the DC demagnetization coil. If the inner diameter of the DC demagnetization coil is small, the magnetic core to be demagnetized needs to be placed on one side of the DC demagnetization coil and needs to be as close to the DC demagnetization coil as possible.

[0018] Preferably, the resistance range of the adjustable resistor is 1Ω to 200Ω, for example, 1Ω, 2Ω, 5Ω, 8Ω, 10Ω, 20Ω, 50Ω, 80Ω, 100Ω, 120Ω, 150Ω, 180Ω, 200Ω, etc. The present invention adjusts the resistance range of the adjustable resistor so that the current in the DC demagnetization coil increases continuously, thereby increasing the magnetic field to cause the internal magnetic domains of the magnetic core to be demagnetized to rotate.

[0019] Preferably, the DC demagnetization circuit further includes a conducting wire.

[0020] Preferably, the diameter of the wire is 4 mm to 16 mm, for example, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, etc.

[0021] In a second aspect, the present invention provides a method for demagnetizing using the DC demagnetization circuit according to the first aspect, the method comprising the following steps:

[0022] S1. Control the power supply unit to output a forward voltage, adjust the resistance adjustment unit to a maximum resistance value, place the product to be demagnetized at the DC demagnetization unit, and adjust the resistance value of the resistance adjustment unit from large to small after the switching unit closes the circuit to form a forward current from small to large;

[0023] S2. Use the switching unit to disconnect the circuit, control the power supply unit to output a reverse voltage, and adjust the resistance adjustment unit to the maximum resistance value again. After using the switching unit to close the circuit, adjust the resistance value of the resistance adjustment unit again from large to small to form a reverse current from small to large until all the residual magnetism of the product to be demagnetized is removed.

[0024] Preferably, in step S1, the product to be demagnetized is placed inside or on one side of the DC demagnetization unit.

[0025] In the present invention, the product to be demagnetized is placed inside the DC demagnetization unit, preferably in the central area of ​​the DC demagnetization unit.

[0026] Preferably, in step S1 , the direction of the forward magnetic field generated by the forward current applied to the DC demagnetization unit on the product to be demagnetized is the same as the direction of the residual magnetic field.

[0027] Preferably, the resistance value of the resistance adjustment unit is adjusted from large to small in step S1 until the magnetic field value of the product to be demagnetized is not less than 400 Gauss, for example, it can be 400 Gauss, 420 Gauss, 450 Gauss, 480 Gauss, 500 Gauss, 520 Gauss, 550 Gauss, 580 Gauss, 600 Gauss, 700 Gauss, etc.

[0028] Preferably, the reverse magnetic field generated by the reverse current applied to the DC demagnetization unit in step S2 on the product to be demagnetized is in a direction opposite to the direction of the residual magnetic field.

[0029] Preferably, in step S2, the resistance value of the resistance adjustment unit is adjusted again from large to small until the reverse magnetic field value of the product to be demagnetized is not less than 400 Gauss, and the reverse magnetic field value is the same as the forward magnetic field value, for example, it can be 400 Gauss, 420 Gauss, 450 Gauss, 480 Gauss, 500 Gauss, 520 Gauss, 550 Gauss, 580 Gauss, 600 Gauss, 700 Gauss, etc.

[0030] In a third aspect, the present invention provides a DC demagnetization device, comprising the DC demagnetization circuit according to the first aspect.

[0031] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention provides a direct current demagnetization circuit, which forms an alternating magnetic field on a direct current demagnetization unit by designing the composition of the direct current demagnetization circuit, and in particular, applies a reverse magnetic field in the opposite direction to the original residual magnetism, so as to completely eliminate the residual magnetism in the magnetic core element. This direct current demagnetization circuit requires that the strength of the reverse magnetic field applied is sufficient to cover all magnetic domains of the product to be demagnetized, so as to ensure that each magnetic region in the product can be fully demagnetized, thereby eliminating all residual magnetism, further improving the application scope and demagnetization effect of the magnetic core demagnetization. In addition, the overall direct current demagnetization circuit structure provided by the present invention is simple and practical, and can achieve demagnetization within just a few cycles, with high speed and high efficiency. At the same time, the direct current demagnetization circuit provided by the present invention is easy to use repeatedly in actual products, has no special requirements for product structure and function, and has strong applicability, thereby solving the technical problem that the existing demagnetization method requires the magnetic core to stop working or even cannot be directly operated in the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of a DC demagnetization circuit provided by the present invention.

[0035] Figure 2 It is a schematic diagram of the structure of the product to be demagnetized.

[0036] Figure 3 It is a schematic diagram of subjecting the product to be demagnetized to a DC bias test. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below by combining the accompanying drawings and specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0038] Example 1

[0039] This embodiment provides a DC demagnetization circuit, such as Figure 1 As shown, the DC demagnetization circuit includes a DC power supply, a DC demagnetization coil, a switch element, and an adjustable resistor which are electrically connected in series in sequence by a wire. Specifically, one end of the DC demagnetization coil is connected to one end of the DC power supply, the other end of the DC demagnetization coil is connected to one end of the switch element, the other end of the switch element is connected to one end of the adjustable resistor, and the other end of the adjustable resistor is connected to the other end of the DC power supply.

[0040] Among them, the output voltage range of the DC power supply is 12V; the number of turns of the DC demagnetization coil is 9 turns; the inner diameter of the DC demagnetization coil is 50mm; the resistance range of the adjustable resistor is 100Ω~160Ω; and the diameter of the wire is 7mm.

[0041] This embodiment also provides a method for demagnetizing using the above DC demagnetization circuit, which includes the following steps:

[0042] S1. Control the DC power supply output to a positive voltage, and adjust the adjustable resistor to the maximum resistance value. Figure 2 The product to be demagnetized is placed in the center area of ​​the DC demagnetization coil. After the circuit is closed by the switch element, the resistance value of the adjustable resistor is adjusted from large to small until the magnetic field value of the product to be demagnetized is 400 Gauss, so as to form a forward current from small to large, and the direction of the forward magnetic field generated by the forward current on the product to be demagnetized is the same as the direction of the residual magnetic field;

[0043] S2. Use the switch element to disconnect the circuit, control the DC power supply to output a reverse voltage, and adjust the adjustable resistor to the maximum resistance value again. Use the switch element to close the circuit and adjust the resistance value of the adjustable resistor again from large to small until the reverse magnetic field value of the product to be demagnetized is 400 Gauss, so as to form a reverse current from small to large, and the direction of the reverse magnetic field generated by the reverse current on the product to be demagnetized is opposite to the direction of the residual magnetic field until all the residual magnetism of the product to be demagnetized is removed.

[0044] Example 2

[0045] The present embodiment provides a DC demagnetization circuit, which includes a DC power supply, a DC demagnetization coil, a switch element, and an adjustable resistor that are electrically connected in series in sequence using a wire. Specifically, one end of the DC demagnetization coil is connected to one end of the DC power supply, the other end of the DC demagnetization coil is connected to one end of the switch element, the other end of the switch element is connected to one end of the adjustable resistor, and the other end of the adjustable resistor is connected to the other end of the DC power supply.

[0046] Among them, the voltage range of the DC power supply is 36V; the number of turns of the DC demagnetization coil is 15 turns; the inner diameter of the DC demagnetization coil is 5mm; the resistance range of the adjustable resistor is 10Ω~50Ω; and the diameter of the wire is 12mm.

[0047] This embodiment also provides a method for demagnetizing using the above DC demagnetization circuit, which includes the following steps:

[0048] S1. Control the DC power supply to output a forward voltage, adjust the adjustable resistor to the maximum resistance value, place the product to be demagnetized in the center area of ​​the DC demagnetization coil, close the circuit using the switch element, and adjust the resistance value of the adjustable resistor from large to small until the magnetic field value of the product to be demagnetized is 500 Gauss, so as to form a forward current from small to large, and the direction of the forward magnetic field generated by the forward current on the product to be demagnetized is the same as the direction of the residual magnetic field;

[0049] S2. Use the switch element to disconnect the circuit, control the DC power supply to output a reverse voltage, and adjust the adjustable resistor to the maximum resistance value again. Use the switch element to close the circuit and adjust the resistance value of the adjustable resistor again from large to small until the reverse magnetic field value of the product to be demagnetized is 500 Gauss, so as to form a reverse current from small to large, and the direction of the reverse magnetic field generated by the reverse current on the product to be demagnetized is opposite to the direction of the residual magnetic field until all the residual magnetism of the product to be demagnetized is removed.

[0050] Example 3

[0051] The present embodiment provides a DC demagnetization circuit, which includes a DC power supply, a DC demagnetization coil, a switch element, and an adjustable resistor that are electrically connected in series in sequence using a wire. Specifically, one end of the DC demagnetization coil is connected to one end of the DC power supply, the other end of the DC demagnetization coil is connected to one end of the switch element, the other end of the switch element is connected to one end of the adjustable resistor, and the other end of the adjustable resistor is connected to the other end of the DC power supply.

[0052] Among them, the voltage range of the DC power supply is 28V; the number of turns of the DC demagnetization coil is 3 turns; the inner diameter of the DC demagnetization coil is 60mm; the resistance range of the adjustable resistor is 150Ω~200Ω; and the diameter of the wire is 4mm.

[0053] This embodiment also provides a method for demagnetizing using the above DC demagnetization circuit, which includes the following steps:

[0054] S1. Control the DC power supply to output a forward voltage, adjust the adjustable resistor to the maximum resistance value, place the product to be demagnetized in the center of the DC demagnetization coil, close the circuit using the switch element, and adjust the resistance value of the adjustable resistor from large to small until the magnetic field value of the product to be demagnetized is 600 Gauss, so as to form a forward current from small to large, and the direction of the forward magnetic field generated by the forward current on the product to be demagnetized is the same as the direction of the residual magnetic field;

[0055] S2. Use the switch element to disconnect the circuit, control the DC power supply to output a reverse voltage, and adjust the adjustable resistor to the maximum resistance value again. Use the switch element to close the circuit and adjust the resistance value of the adjustable resistor again from large to small until the reverse magnetic field value of the product to be demagnetized is 600 Gauss, so as to form a reverse current from small to large, and the direction of the reverse magnetic field generated by the reverse current on the product to be demagnetized is opposite to the direction of the residual magnetic field until all the residual magnetism of the product to be demagnetized is removed.

[0056] Example 4

[0057] The present embodiment provides a DC demagnetization circuit, which includes a DC power supply, a DC demagnetization coil, a switch element, and an adjustable resistor that are electrically connected in series in sequence using a wire. Specifically, one end of the DC demagnetization coil is connected to one end of the DC power supply, the other end of the DC demagnetization coil is connected to one end of the switch element, the other end of the switch element is connected to one end of the adjustable resistor, and the other end of the adjustable resistor is connected to the other end of the DC power supply.

[0058] Among them, the voltage range of the DC power supply is 48V; the number of turns of the DC demagnetization coil is 3 turns; the inner diameter of the DC demagnetization coil is 3mm; the resistance range of the adjustable resistor is 1Ω~25Ω; and the diameter of the wire is 16mm.

[0059] This embodiment also provides a method for demagnetizing using the above DC demagnetization circuit, which includes the following steps:

[0060] S1. Control the DC power supply to output a forward voltage, adjust the adjustable resistor to a maximum resistance value, place the product to be demagnetized in the center of the DC demagnetization coil, close the circuit using the switch element, and adjust the resistance value of the adjustable resistor from large to small until the magnetic field value of the product to be demagnetized is 400 Gauss, so as to form a forward current from small to large, and the direction of the forward magnetic field generated by the forward current on the product to be demagnetized is the same as the direction of the residual magnetic field;

[0061] S2. Use the switch element to disconnect the circuit, control the DC power supply to output a reverse voltage, and adjust the adjustable resistor to the maximum resistance value again. Use the switch element to close the circuit and adjust the resistance value of the adjustable resistor again from large to small until the reverse magnetic field value of the product to be demagnetized is 400 Gauss, so as to form a reverse current from small to large, and the direction of the reverse magnetic field generated by the reverse current on the product to be demagnetized is opposite to the direction of the residual magnetic field until all the residual magnetism of the product to be demagnetized is removed.

[0062] Example 5

[0063] The present embodiment provides a DC demagnetization circuit, which includes a DC power supply, a DC demagnetization coil, a switch element, and an adjustable resistor that are electrically connected in series in sequence using a wire. Specifically, one end of the DC demagnetization coil is connected to one end of the DC power supply, the other end of the DC demagnetization coil is connected to one end of the switch element, the other end of the switch element is connected to one end of the adjustable resistor, and the other end of the adjustable resistor is connected to the other end of the DC power supply.

[0064] Among them, the voltage range of the DC power supply is 24V; the number of turns of the DC demagnetization coil is 12 turns; the inner diameter of the DC demagnetization coil is 25mm; the resistance range of the adjustable resistor is 30Ω~80Ω; and the diameter of the wire is 10mm.

[0065] This embodiment also provides a method for demagnetizing using the above DC demagnetization circuit, which includes the following steps:

[0066] S1. Control the DC power supply to output a forward voltage, adjust the adjustable resistor to a maximum resistance value, place the product to be demagnetized in the center of the DC demagnetization coil, close the circuit using the switch element, and adjust the resistance value of the adjustable resistor from large to small until the magnetic field value of the product to be demagnetized is 400 Gauss, so as to form a forward current from small to large, and the direction of the forward magnetic field generated by the forward current on the product to be demagnetized is the same as the direction of the residual magnetic field;

[0067] S2. Use the switch element to disconnect the circuit, control the DC power supply to output a reverse voltage, and adjust the adjustable resistor to the maximum resistance value again. Use the switch element to close the circuit and adjust the resistance value of the adjustable resistor again from large to small until the reverse magnetic field value of the product to be demagnetized is 400 Gauss, so as to form a reverse current from small to large, and the direction of the reverse magnetic field generated by the reverse current on the product to be demagnetized is opposite to the direction of the residual magnetic field until all the residual magnetism of the product to be demagnetized is removed.

[0068] Example 6

[0069] The difference between this embodiment and the first embodiment is that the number of turns of the DC demagnetization coil is 25, and the rest is the same as the first embodiment.

[0070] Example 7

[0071] The difference between this embodiment and the first embodiment is that the inner diameter of the DC demagnetization coil is 8 mm, and the rest is the same as the first embodiment.

[0072] Example 8

[0073] The difference between this embodiment and the first embodiment is that the inner diameter of the DC demagnetization coil is 15 mm, and the rest is the same as the first embodiment.

[0074] Example 9

[0075] The difference between this embodiment and the first embodiment is that the resistance range of the adjustable resistor is 1Ω to 250Ω, and the rest is the same as the first embodiment.

[0076] Comparative Example 1

[0077] This comparative example provides a demagnetization method, which comprises the following steps:

[0078] The product to be demagnetized is heated to a Curie temperature of 160°C and kept warm for 30 minutes to remove the residual magnetism of the product to be demagnetized.

[0079] Test conditions

[0080] The product to be demagnetized provided in Example 4 is subjected to a DC bias test. The schematic diagram of the test is shown in FIG. Figure 3 shown.

[0081] Through the DC bias test with superimposed current of 0A, 1A, 2A, 4A, 6A, 10A, 16A and 22A, the inductance after the DC bias test and the inductance after the DC bias test with the DC bias turned off are tested. The test results are shown in Table 1:

[0082] Table 1

[0083]

[0084] It can be seen from Table 1 that when a saturation current of 22A is applied, the inductance of the product to be demagnetized drops to 7.59μH, which is 65.9% of the inductance (11.52μH) of the product to be demagnetized before saturation. In addition, the present invention re-measures the inductance of the product to be demagnetized on the second, third, fourth, sixth and tenth days, and the corresponding inductances are 7.60μH, 7.62μH, 7.63μH, 7.63μH and 7.66μH, respectively. Therefore, it can be seen that the inductance of the product to be demagnetized cannot be naturally restored.

[0085] The products to be demagnetized provided in Examples 1 to 9 and Comparative Example 1 were demagnetized, and the changes in inductance and the recovery rates before and after the demagnetization are shown in Table 2:

[0086] Table 2

[0087]

[0088] As can be seen from Table 2, the present invention uses a DC demagnetization circuit with a specific structure for demagnetization. Specifically, by applying a magnetic field in the forward direction and then applying a reverse magnetic field of the same value in the reverse direction, the magnetic core can be quickly demagnetized, and the inductance can be restored to more than 90%. Compared with the demagnetization solution of heating to the Curie temperature, the DC demagnetization method provided by the present invention can protect the plastic parts in the circuit from deformation and avoid damage to other electronic components that cannot withstand a temperature of 160°C.

[0089] In addition, the DC demagnetization circuit provided by the present invention is easy to use repeatedly in actual products, has no special requirements on product structure and function, and has strong applicability, thereby solving the technical problem that the existing demagnetization method requires the magnetic core to stop working or even cannot be directly operated in the product.

[0090] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention are within the protection scope and disclosure scope of the present invention.

Claims

1. A DC demagnetization circuit, characterized in that: The DC demagnetization circuit comprises a power supply unit, a DC demagnetization unit, a switching unit and a resistance adjustment unit, wherein the power supply unit, the DC demagnetization unit, the switching unit and the resistance adjustment unit are sequentially connected in series to form a closed loop; The DC demagnetization circuit removes all residual magnetism of the product to be demagnetized by applying a demagnetization current with alternating polarity to both ends of the DC demagnetization unit.

2. The DC demagnetization circuit according to claim 1, characterized in that: The power supply unit includes a DC power supply; Preferably, the DC demagnetization unit comprises a DC demagnetization coil; Preferably, the switching unit comprises a switch element; Preferably, the resistance adjustment unit comprises an adjustable resistor; Preferably, one end of the DC demagnetization coil is connected to one end of the DC power supply, the other end of the DC demagnetization coil is connected to one end of the switching element, the other end of the switching element is connected to one end of the adjustable resistor, and the other end of the adjustable resistor is connected to the other end of the DC power supply.

3. The DC demagnetization circuit according to claim 2, characterized in that: The output voltage range of the DC power supply is 12V to 48V; Preferably, the number of turns of the DC demagnetization coil is 3 to 15 turns; Preferably, the inner diameter of the DC demagnetization coil is 3 mm to 60 mm, preferably 5 mm to 8 mm; Preferably, the resistance range of the adjustable resistor is 1Ω to 200Ω.

4. The DC demagnetization circuit according to any one of claims 1 to 3, characterized in that: The DC demagnetization circuit also includes a conductor; Preferably, the diameter of the wire is 4 mm to 16 mm.

5. A method for demagnetizing using the DC demagnetization circuit according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1. Control the power supply unit to output a forward voltage, adjust the resistance adjustment unit to a maximum resistance value, place the product to be demagnetized at the DC demagnetization unit, and adjust the resistance value of the resistance adjustment unit from large to small after the switching unit closes the circuit to form a forward current from small to large; S2. Use the switching unit to disconnect the circuit, control the power supply unit to output a reverse voltage, and adjust the resistance adjustment unit to the maximum resistance value again. After using the switching unit to close the circuit, adjust the resistance value of the resistance adjustment unit again from large to small to form a reverse current from small to large until all the residual magnetism of the product to be demagnetized is removed.

6. The method according to claim 5, characterized in that In step S1, the product to be demagnetized is placed inside or on one side of the DC demagnetization unit; Preferably, in step S1 , the direction of the forward magnetic field generated by the forward current applied to the DC demagnetization unit on the product to be demagnetized is the same as the direction of the residual magnetic field.

7. The method according to claim 5 or 6, characterized in that: In step S1, the resistance value of the resistance adjustment unit is adjusted from large to small until the magnetic field value of the product to be demagnetized is not less than 400 Gauss.

8. The method according to any one of claims 5 to 7, characterized in that: In step S2, the reverse current applied to the DC demagnetization unit generates a reverse magnetic field on the product to be demagnetized, the direction of which is opposite to the direction of the residual magnetic field.

9. The method according to any one of claims 5 to 8, characterized in that: In step S2, the resistance value of the resistance adjustment unit is adjusted again from large to small until the reverse magnetic field value of the product to be demagnetized is not less than 400 Gauss, and the reverse magnetic field value is the same as the forward magnetic field value.

10. A DC demagnetization device, characterized in that: The DC demagnetization device comprises a DC demagnetization circuit according to any one of claims 1 to 4.

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