CN101110292A - Filter element and manufacturing method thereof - Google Patents

Abstract

The invention discloses a filter element and a manufacturing method thereof, the filter element can simultaneously have the function of filtering common mode noise and differential mode noise, and the filter element comprises a common mode filter, a second iron core and a container for forming. The common mode filter comprises a first iron core and at least one winding, and the winding surrounds the outside of the first iron core. The second iron core is completely coated outside the common-mode filtering piece. The common mode filter and the second iron core are both arranged in the container for molding, and the first iron core and the second iron core respectively have different initial magnetic permeability values .

Description

Filter element and manufacturing method thereof

technical field

The invention relates to a filter element and a manufacturing method thereof, in particular to a filter element capable of filtering both common-mode noise and differential-mode noise and a manufacturing method thereof.

Background technique

Nowadays, people use electrical appliances very frequently, and the use of electrical appliances will inevitably use power to make the electrical appliances operate normally. However, when electrical appliances use AC power, the operation of power supply, high-frequency transformer or other components' parasitic capacitance or stray capacitance may cause the current supplied by the AC power to carry noise current. This is the phenomenon of electromagnetic interference.

Generally speaking, the noise generated by the use of AC power includes differential mode noise and common mode noise, and the EMI filter circuit can be used as the first line of defense against electromagnetic radiation for the power supply, mainly composed of choke Composed of a coil (choke coil) and a capacitor (capacitor), the role of the choke coil is to suppress noise generation or entry into electronic instruments or equipment. Please refer to FIG. 1A , which is a schematic diagram of an iron core of US Patent Publication No. 4,587,507. In FIG. 1A, the iron core 1 of the conventional choke coil is made of an amorphous metal alloy (amorphous metallic alloy) thin strip. Since the frequency of use of amorphous metal alloys is usually lower than 100 kilohertz (kHz), and its DC-bias resistance is also poor, an air gap (air gap) 2 is designed in the iron core 1 in an attempt to improve DC resistance. -The disadvantage of poor bias characteristics. However, this method will greatly reduce the initial permeability of the choke coil.

Please refer to FIG. 1B , which is a schematic diagram of an iron core of US Patent Publication No. 6,456,182. In order to eliminate common mode noise, the method disclosed in US Patent Publication No. 6,456,182 uses three independent iron cores 11a, 11b, 11c to form a choke coil for eliminating common mode noise. The material of the iron cores 11a, 11b, 11c is an oxidized magnetic substance, and the iron cores are separated by insulating material or glue between the iron cores, and the size resonance phenomenon of the three independent iron cores 11a, 11b, 11c can be used to make them The operating frequency is extended to 10MHz, so that noise can be effectively reduced from 10kHz to 10MHz. However, this method of stacking three iron cores will increase the overall height of the choke coil, which is not conducive to the trend of miniaturization. In addition, this kind of choke coil can only be used to eliminate common mode noise, and cannot eliminate differential mode noise.

Please refer to FIG. 1C , which is a schematic diagram of an iron core of US Patent Publication No. 5,581,224. In order to be able to eliminate common mode noise and differential mode noise at the same time, a choke coil is disclosed in US Patent No. 5,581,224, which is mainly composed of two independent iron cores, namely the outer iron core 111 and the inner iron core The iron core 114 is formed by winding the winding wire 18. The iron core 111 is made of magnetic ferrite or amorphous material, and the iron core 114 is a dust core with low magnetic permeability. The iron cores 111 and 114 are separated by an insulating material. Utilize the characteristics of high magnetic permeability of the iron core 111 to filter out the common mode noise, and utilize the characteristics of the low magnetic permeability of the iron core 114 to filter out part of the differential mode noise, however, this way of arranging two independent iron cores will The area occupied by the entire choke coil is quite large, which is not conducive to miniaturization. Moreover, since an insulating material must be coated between the two independent iron cores to separate them, not only the material cost is increased, but also the structure requires manual assembly, which consumes man-hours. Furthermore, since the iron core is prone to generate leakage inductance and affect the surrounding components, and the iron core itself is also easily affected by the surrounding magnetic field, making the characteristics of the components unstable.

Therefore, how to make a choke coil that can effectively eliminate common-mode noise and differential-mode noise at the same time, and can conform to the trend of miniaturization of the overall volume under the consideration of economic cost, is an urgent research direction for people in this field. .

Contents of the invention

Therefore, in order to solve the above problems, the present invention proposes a filter element and a manufacturing method thereof, which can effectively eliminate common-mode noise and differential-mode noise at the same time, and effectively improve the filtering effect. In addition, since the noise of differential mode and common mode can be eliminated in the same filter element, the cost and the occupied volume can be effectively reduced.

According to the purpose of the present invention, a filter element is proposed, which includes a common mode filter element, a second iron core and a molding container. The common mode filter includes a first iron core and at least one winding wire, and the winding wire is wound around the outside of the first iron core. The second iron core is completely covered outside the common mode filter. Wherein the common-mode filter element and the second iron core are located in the molding container, and the first iron core and the second iron core have different initial magnetic permeability values (μ) respectively.

According to another object of the present invention, another method for manufacturing a filter element is provided, including: providing a common mode filter, including a first iron core and at least one winding, and the winding is wound around the outside of the first iron core; The common-mode filter is placed in a molding container; pouring a magnetic slurry into the molding container and filling the molding container; and performing a curing procedure; wherein the magnetic slurry is formed after the curing procedure A second iron core is completely wrapped around the common mode filter, and the first iron core and the second iron core have different initial magnetic permeability values (μ).

As in the above filter element and its manufacturing method, the material of the first iron core includes magnetic ferrite, and the material of the second iron core is a magnetic slurry. The magnetic slurry includes a magnetic filler and a resin, and the resin is a thermosetting resin or a photocurable resin. The magnetic filler includes a magnetic powder of pure iron, ferromagnetic metal alloy, manganese-zinc ferrite, or nickel-zinc ferrite, and the ferromagnetic metal alloy includes iron-silicon alloy, iron-cobalt alloy, sendust alloy, or iron-nickel alloy. Moreover, the weight percentage of the magnetic filler in the magnetic slurry is about 0% to 95%. In addition, an insulating casing is further included outside the first iron core, and the winding wires respectively surround the first iron core and the outside of the insulating casing. In addition, the first iron core is formed by injection molding or powder pressure molding, and the second iron core is formed by grouting and solidification. The filter element mentioned above can be applied to a choke coil, a power supply, an inductor or an electronic device that generates noise, and can eliminate a common mode noise and a differential mode noise.

In order to make the above and other objects, features, and advantages of the present invention more comprehensible, a preferred embodiment is specifically cited below, together with the accompanying drawings, and is described in detail as follows:

Description of drawings

FIG. 1A is a schematic diagram of the iron core of the existing U.S. Patent Publication No. 4,587,507;

FIG. 1B is a schematic diagram of the iron core of the existing US Patent No. 6,456,182;

FIG. 1C is a schematic diagram of the iron core of the existing US Patent No. 5,581,224;

Fig. 2A to Fig. 2C are each schematic diagram when the filter element of preferred embodiment of the present invention is made;

FIG. 3 is a schematic diagram of a common-mode filter element in a filter element according to a preferred embodiment of the present invention.

Description of main component symbols:

1, 11a, 11b, 11c, 111, 114,: iron core

18: Winding

2: air gap

20: filter element

22: Second core

24: Forming container

30: Common mode filter

32: The first iron core

34: shell

36: Winding

38a, 38b, 38c, 38d: outlet

Detailed ways

Please refer to FIG. 2A, FIG. 2B, FIG. 2C and FIG. 3 at the same time. FIG. 2A to FIG. 2C are schematic diagrams of the filter elements produced according to the preferred embodiment of the present invention, and FIG. 3 is the filter element of the preferred embodiment of the present invention. Schematic diagram of the common-mode filter element. The filter element 20 disclosed in the preferred embodiment of the present invention can be applied to a choke coil as a filter for a power supply, an inductor, or other electronic devices that may generate noise. Alternatively, the filter element mentioned above can also be used to make an inductor, which can also achieve the function of miniaturizing the inductor. The filter element 20 mainly includes a common mode filter element 30 , a second iron core 22 and a molding container 24 . The common mode filter 30 includes a first iron core 32 , an insulating shell 34 and two sets of winding wires 36 . The first iron core 32 is formed by injection molding or powder pressure molding, and the insulating shell 34 is wrapped around the first iron core 32 to increase insulation and prevent the first iron core 32 from interfering with the first iron core 22. A short circuit occurs due to contact, and the characteristics of withstand voltage can be improved.

The two sets of winding wires 36 wrap around the first iron core 32 and the outer shell 34 respectively, and have four outgoing wires 38a, 38b, 38c, 38d. The second iron core 22 is formed by grouting and curing, and the second iron core 22 completely covers the outside of the common mode filter 30 . Wherein the common mode filter element 30 and the second iron core 22 are located in the molding container 24 .

In addition, the preferred embodiment of the present invention proposes a manufacturing method of the filter element 20, including: providing a common mode filter element 30, including a first iron core 32 and two sets of winding wires 36, and the two sets of winding wires 36 are respectively wound around The outside of the first iron core 32; the common mode filter 30 is put into a molding container 24, the molding container 24 is a container with a predetermined space in the center, and the size of the space corresponds to the subsequent to be made to form The size of the second iron core 22; pour a magnetic slurry into the molding container 24 and fill the molding container 24; and carry out a curing (curing) procedure; wherein, after the curing procedure, the magnetic slurry forms a The second iron core 22 is completely wrapped around the common mode filter 30 , and only four outgoing lines 38 a , 38 b , 38 c , 38 d are left to pass through the second iron core 22 for electrical connection with external components.

The first iron core 32 of the common mode filter 30 and the second iron core 22 covered therewith have different initial magnetic permeability values (μ) respectively, and because the magnetic permeability of the second iron core 22 is higher than that of the first iron core The magnetic permeability of 32 is low, which can be used to filter out differential mode noise, and for the first iron core 32 made of magnetic ferrite, its high magnetic permeability can be used to filter out common mode noise. Therefore, only a single filter element 20 can be used to eliminate the differential mode and common mode noise, thereby effectively reducing the cost. Furthermore, since the common-mode filter element 30 is embedded in the second iron core 22 , the overall volume of the filter element 20 can meet the trend of thinner, smaller, and miniaturized due to the embedded design.

As in the aforementioned filter element 20 and its manufacturing method, the material of the first iron core 32 includes magnetic ferrite, and the material of the second iron core 22 is a magnetic paste. The magnetic slurry includes a magnetic filler and a resin, and the resin is a thermosetting resin or a photocurable resin. The magnetic filler includes a magnetic powder of pure iron, ferromagnetic metal alloy, manganese-zinc ferrite, or nickel-zinc ferrite, and the ferromagnetic metal alloy includes iron-silicon alloy, iron-cobalt alloy, sendust alloy, or iron-nickel alloy. The magnetic filler accounts for more than 10% and less than 98% by weight of the magnetic slurry.

The following will present various experimental data for the second iron core 22 made of different magnetic slurries, and make a relative comparison with the existing choke coils that can only eliminate common mode noise.

The first type of magnetic filler (ferromagnetic metal alloy)

Using the above-mentioned manufacturing method, various magnetic powders of ferromagnetic metal alloys are used, and the magnetic slurry is prepared with resin, and the concentration thereof is 85% by weight. The various experimental data obtained are shown in the table below.

DM insertion loss (dB) DM resonance frequency (MHz) DM inductance value (μH)@10KHz Existing 20.1@30MHz Greater than 30 6.38 Trivalent iron silicon alloy 40 18.9 12.23 Hexavalent iron silicon alloy 41.1 18.6 12.17 Iron Cobalt Alloy 40.2 21.3 10.68 Iron-nickel alloy 40.5 17.5 12.73

As can be seen from the above table, the filter element according to the preferred embodiment of the present invention has an increase in the inductance value of the differential mode noise (Differential mode noise, DM noise) compared to the existing choke coils that can only eliminate common mode noise. It is about doubled, so the effect is very obvious. In addition, in terms of differential mode noise (DM) insertion loss, the filtering element according to the preferred embodiment of the present invention is about double that of the existing choke coil that can only eliminate common mode noise.

The second type of magnetic filler (manganese-zinc ferrite)

Using the above manufacturing method, the magnetic slurry is prepared by using manganese-zinc ferrite magnetic powders with different initial magnetic permeability values (μ) together with resin, and the concentration is about 80%-85% by weight. The various experimental data obtained are shown in the table below.

DM insertion loss (dB) DM resonance frequency (MHz) DM inductance value (μH)@10KHz Existing 20.1@30MHz Greater than 30 6.38 Manganese-zinc ferrite-A10 37.5 19.3 14.06 Manganese-zinc ferrite-A05 38.9 18.6 14.53

Among them, A10 means its initial magnetic permeability value (μ) is 10000, and A05 means its initial magnetic permeability value (μ) is 5000. As can be seen from the above table, the filter element according to the preferred embodiment of the present invention has a characteristic of the inductance value of differential mode noise (DM noise), which is two times greater than that of the existing choke coil that can only eliminate common mode noise. times, so the effect is very obvious. In addition, in terms of differential mode noise (DM) insertion loss, the filter element according to the preferred embodiment of the present invention is also about twice that of the existing choke coils that can only eliminate common mode noise, and due to the The DM insertion loss exhibited by the filter element of the preferred embodiment can be nearly 40 decibels (dB), exhibiting good differential mode filtering characteristics.

The third type of magnetic filler (nickel-zinc ferrite)

Using the above manufacturing method, using nickel-zinc ferrite magnetic powders with different initial magnetic permeability values (μ), together with resin, the magnetic slurry is prepared with a concentration of about 85% by weight. The various experimental data obtained are shown in the table below.

DM insertion loss (dB) DM resonance frequency (MHz) DM inductance value (μH)@10KHz Existing 20.1@30MHz Greater than 30 6.38 Nickel-zinc ferrite-R7 38.7 28.8 10.5 Nickel-zinc ferrite-K22 28.9@30MHz Greater than 30 7.37

Among them, R7 means that its initial magnetic permeability value (μ) is 1500, and K22 means that its initial magnetic permeability value (μ) is 350. As can be seen from the above table, the filter element according to the preferred embodiment of the present invention has a better effect than the existing choke coils that can only eliminate common mode noise in terms of the inductance value of differential mode noise (DM noise). Good to come. In addition, in terms of differential mode noise (DM) insertion loss, the filter element according to the preferred embodiment of the present invention is also about twice that of the existing choke coils that can only eliminate common mode noise, and due to the The DM insertion loss exhibited by the filter element of the preferred embodiment can be nearly 40 decibels (dB), and is close to 30 MHz at a higher frequency position, showing good differential mode filtering characteristics. .

To sum up, the filter element of the preferred embodiment of the present invention can effectively eliminate common mode noise and differential mode noise at the same time, and effectively improve the filtering effect. In addition, since the noise of the differential mode and the common mode can be eliminated in the same filter element, the cost and the occupied volume can be effectively reduced, which conforms to the trend of thinner, smaller and miniaturized. Furthermore, the existing problem of affecting the surrounding components due to the leakage inductance of the iron core can be avoided, and the problem of unstable characteristics of the components caused by the influence of the surrounding magnetic field on the existing iron core itself can be avoided.

Although the present invention has been disclosed in conjunction with the above preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make various modifications and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.

Claims (19)

1. A filter element, comprising: A common mode filter, including a first iron core and at least one winding, and the winding is wound outside the first iron core; and a second iron core completely covering the outside of the common mode filter; Wherein the first iron core and the second iron core have different initial magnetic permeability values (μ). 2. The filter element as claimed in claim 1, wherein the material of the first iron core comprises magnetic ferrite, and the material of the second iron core is a magnetic paste. 3. The filter element as claimed in claim 2, wherein the magnetic paste comprises a magnetic filler and a resin. 4. The filter element as claimed in claim 3, wherein the resin is a thermosetting resin or a photocurable resin. 5. The filter element as claimed in claim 3, wherein the magnetic filler comprises a pure iron, a ferromagnetic metal alloy composed of iron-silicon alloy, iron-cobalt alloy, iron-silicon-aluminum alloy, or iron-nickel alloy, manganese- Magnetic powder of zinc ferrite, or nickel-zinc ferrite. 6 . The filter element as claimed in claim 3 , wherein the magnetic filler accounts for more than 10% and less than 98% by weight of the magnetic slurry. 7. The filter element as claimed in claim 1, wherein the first iron core is formed by injection molding or powder pressure molding, and the second iron core is formed by grouting and curing. 8 . The filter element as claimed in claim 1 , further comprising an insulating shell located outside the first iron core, and the winding wire wraps around the first iron core and the outside of the insulating shell. 9 . The filter element as claimed in claim 1 , further comprising a molding container, and the common-mode filter element and the second core are located in the molding container. 10. A manufacturing method of a filter element, comprising: A common mode filter is provided, including a first iron core and at least one winding wire, and the winding wire is wound around the outside of the first iron core; Putting the common mode filter into a molding container; Pour a magnetic slurry into the forming container; and carry out a curing process; Wherein, after the curing process, the magnetic slurry forms a second iron core and completely covers the common mode filter, and the first iron core and the second iron core have different initial magnetic permeability respectively. value (μ). 11. The manufacturing method as claimed in claim 10, wherein the material of the first iron core comprises magnetic ferrite, and the material of the second iron core is the magnetic slurry. 12. The manufacturing method as claimed in claim 10, wherein the magnetic paste comprises a magnetic filler and a resin. 13. The manufacturing method as claimed in claim 12, wherein the resin is a thermosetting resin or a photocurable resin. 14. The manufacturing method as claimed in claim 12, wherein the magnetic filler comprises a pure iron, a ferromagnetic metal alloy composed of iron-silicon alloy, iron-cobalt alloy, iron-silicon-aluminum alloy, or iron-nickel alloy, manganese- Magnetic powder of zinc ferrite, or nickel-zinc ferrite. 15 . The manufacturing method as claimed in claim 12 , wherein the magnetic filler accounts for more than 10% and less than 98% by weight of the magnetic slurry. 16. The manufacturing method as claimed in claim 10, wherein the first iron core is formed by injection molding or powder compression molding, and the second iron core is formed by grouting and solidified. 17. The manufacturing method as claimed in claim 10, further comprising forming an insulating shell outside the first core, and the winding wire is wound around the first core and the insulating shell. 18. The manufacturing method as claimed in claim 10, wherein the filter element can eliminate a common mode noise and a differential mode noise. 19. The manufacturing method of claim 10, wherein the filter element is applied to a choke coil, a power supply, an inductor, or an electronic device that generates noise.

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