JPS6390812A - Balun transformer - Google Patents

Abstract

PURPOSE:To be able to facilitate winding thereby to automate the winding by forming bifilar windings at a plurality of positions on a sintered ferrite core of an open magnetic path structure, and molding the whole outside with resin which contains ferrite powder to form a closed magnetic path structure. CONSTITUTION:Bifilar windings are formed at a plurality of positions on a sintered ferrite core 12 of an open magnetic path structure, and the whole outside is molded with resin 20 which contains ferrite powder to form a closed magnetic path structure. For example, the core 12 which becomes a winding core is formed by aligning two winding holes 14, and forming slits 16 axially of the respective holes 14 in the wall. Wiring blanks 18 are wound on the core 12 by utilizing the slits 16 to form bifilar windings to form two independent linear transformers in such a manner that one side is connected in series and the other is connected in parallel. Then, the outside is molded with magnetic composite body 20 formed by mixing the ferrite powder and the curable resin.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a balun transformer used for impedance M matching in television receivers, etc., and more specifically to a sintered ferrite magnetic core with an open magnetic path structure. This relates to a balun transformer in which a predetermined bifilar winding is applied to the balun transformer, and the outside thereof is covered with a magnetic composite made of a mixture of ferrite powder and resin.

[Prior art] Television receiver or VTI? A balun transformer is incorporated in the antenna input circuit for impedance matching. The output impedance of the antenna and the characteristic impedance of the feeder are normally 300Ω balanced type, but the impedance of the tuner input circuit is 75Ω.
The unbalanced form of is often used. The balun transformer is a balanced/unbalanced conversion transformer for coupling the two, and also performs impedance matching at the same time.

In principle, two independent line-type transformers are connected in series on the input side and in parallel on the output side, and two parallel wires are wound in both winding holes of a spectacle-shaped ferrite core. This structure has been widely adopted.

[Problems to be solved by the invention] However, in conventional balun transformers, parallel wires must be passed through each small winding hole in a porous magnetic core, and this winding process cannot be automated, so it is all done manually. However, there were disadvantages of poor productivity and high manufacturing costs.

SUMMARY OF THE INVENTION An object of the present invention is to provide a balun transformer that eliminates the drawbacks of the prior art as described above and allows winding to be easily performed and automation possible.

Means for Solving the Problems] The present invention, which can achieve the above objects, provides a sintered ferrite magnetic core with an open magnetic path structure with bifilar S wires at a plurality of locations, and then coats the entire outside with ferrite powder. This is a balun transformer molded with a resin containing a closed magnetic circuit structure.

In a particularly preferred embodiment, a sintered plastic core with narrow slits formed in the outer wall of each S-line window is used,
There is a structure in which winding is performed using slits.

[Function] Since the magnetic core that serves as the winding core itself basically has an open magnetic path structure, the complicated work of inserting the wire into the winding hole is unnecessary, and winding can be easily done through automation. Since the magnetic core and wire (O), which becomes the 0-turn core, are further covered with a resin containing ferrite powder on the outside, the result is a closed loop n-path structure, which has almost the same balun transformer characteristics as the conventional one ( impedance characteristics, return loss, injection loss, etc.).

[Embodiment] FIG. 1 is an explanatory diagram showing an embodiment of a balun transformer 10 according to the present invention.

In this embodiment, a heart with a structure similar to a conventional eyeglass shape is used. The magnetic core 12 serving as the winding core is a ferrite sintered body having a structure in which two winding holes 14 are arranged side by side. One of the points in which the present invention is significantly different from the prior art is that the magnetic core 12 has an open magnetic path structure. That is, for each winding hole 14 of the magnetic core 12, a slit 16 is formed in the wall thereof in the axial direction of the winding hole. The width of this slit 16 is the wire rod 1 to be used.
8 in diameter. Therefore, it becomes possible to wind the wire 18 around the magnetic core 12 using this slit 16. The winding around the magnetic core 12 is basically bifilar-wound using the same parallel wire material as before, forming two independent line-type transformers, with one side connected in series and the other side connected in series. Connect in parallel.

Then, the outside of these is molded with a magnetic composite 20 made of a mixture of ferrite powder and curable resin, as shown by imaginary lines. This point is the second feature of the present invention.

The sintered magnetic core 12 serving as the winding core has an open magnetic path structure, but after the winding is applied, the entire outside of the core is molded with the magnetic composite 20 containing ferrite powder as described above. It has a closed magnetic circuit structure and can exhibit the necessary characteristics as a balun transformer.

FIG. 2 is a sectional view showing another embodiment of the present invention. Although the embodiment shown in FIG. 1 is an example of a spectacle-shaped (two-hole) magnetic core, the present invention is equally applicable to a conventional four-hole structure. Since the basic idea is the same as that of the embodiment shown in FIG. 1 above, corresponding parts are given the same reference numerals.

In this case, the magnetic core 12 has a cross-sectional structure as shown in FIG. 2, is provided with a predetermined winding 18, and is molded with a magnetic composite 20 containing the ferrite powder.

Although the preferred embodiments of the present invention have been described above in detail, the present invention is not limited to such a structure, and the shape of the magnetic core can be changed as appropriate depending on the winding state and the like.

[Effects of the Invention] As described above, the present invention uses a sintered ferrite magnetic core with an open magnetic path structure as a winding core, and performs a predetermined bifilar winding thereon.
Since the balun transformer is molded with resin containing ferrite powder, it is extremely easy to wind the wire, reducing the time required for winding work compared to conventional technology that involves inserting the wire into a small through hole. Since it is also possible to make it into an automatic VJ, it has the effect of significantly reducing manufacturing costs.

In addition, in the present invention, although the winding core has an open magnetic path structure, since the outside is covered with resin containing ferrite powder, it essentially has a closed θ magnetic path structure, and has good balun transformer characteristics equivalent to conventional products. can be expressed.

[Brief explanation of the drawing]

FIG. 1 is an explanatory view showing one embodiment of a balun transformer according to the present invention, and FIG. 2 is a sectional view showing another embodiment of the present invention. lO...Balun transformer, 12...Magnetic core, 14...
・Windling thread hole, 16...Slit, 18...Wire rod, 20
...Magnetic composite. Patent Applicant Fuji Electrochemical Co., Ltd. Agent Shigeru Miyoshi Figure 1 Figure 2

Claims (1)

[Claims] 1. A balun transformer that has a sintered ferrite magnetic core with an open magnetic path structure, bifilar windings at multiple locations, and the entire outside of the core is molded with resin containing ferrite powder to create a closed magnetic path structure.