JPS62123816A - Composite noise filter - Google Patents

Abstract

PURPOSE:To save number of components and to miniaturize the entire shape by providing input/output lead wires connected to an inner electrode of a cylindrical dielectric and an inner electrode of a magnetic substance and an earth lead wire connected to an external electrode of the said dielectric and an outer electrode of the said magnetic substance. CONSTITUTION:The inner electrode 14 of the cylindrical dielectric 13 is connected to lead wires 11, 12 of the input/output terminals electrically. The lead wires 11, 12 are penetrated in a ferrite core 15 and connected also to the inner electrode 16 electrically. The lead wire 17 being the earth terminal is connected to the outer electrode 23 of the cylindrical dielectric 13 and the outer electrode 18 of the ferrite core 15 electrically. The filter is constituted by one cylindrical capacitor and one ferrite core and the outer electrodes of the ferrite core and the capacitor are used as the earth terminal, then radiation of noise is less.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a noise filter that can be used as a noise countermeasure for, for example, electronic equipment using a microcomputer and each line of its interface.

There is a noise filter shown in FIG. 4 as a conventional noise filter used for noise countermeasures.

In the structure shown in FIG. 5, electrodes are provided on both sides of a disc-shaped dielectric substrate 1, a lead wire having signal input/output terminals 3 and 4 is connected to the non-ground electrode 2, and a cylindrical ferrite bead is connected to the non-ground electrode 2. Cores 5 and 6 are inserted into their respective terminals. Further, the lead wire 7 is a ground terminal and is connected to a ground side electrode provided on the back surface of the dielectric substrate 1 so as to face the non-ground side electrode 2 .

If this is shown as an equivalent circuit, it becomes a T-shaped circuit as shown in FIG. 8,
9 is an inductor made up of ferrite bead cores 5 and 6, and 10 is a bypass capacitor made up of a dielectric substrate 1 and electrodes.

Problems to be Solved by the Invention However, this conventional noise filter uses only one capacitor and two ferride bee cores.
There are a total of 3 pieces.

In addition, a flat plate capacitor is used, and if the capacitance C
Considering the shape to have a dielectric constant Σ5=1000 (pF), the relative dielectric constant Σ5=3000. Assuming that the flat plate thickness is 0.3 (1wI) as the strength limit thickness, the electrode diameter is r (m), and the space gap for leak prevention is 0.5-, then MK
In the S system, the formula is as follows.

C=(r/2)2·Σs10.113t (pF) From this equation, r=3.8 (mm), and the diameter of the dielectric substrate 7 is 4.8 (wn). If the capacitance is constant, reducing the diameter of the dielectric substrate 7 will reduce the thickness, causing the problem of destruction of the dielectric substrate 1, and increasing the thickness will increase the diameter of the dielectric substrate. Furthermore, since two ferrite bead cores are combined with this flat plate capacitor, it is difficult to miniaturize the entire composite.

Furthermore, since a flat plate capacitor is used, the live portion, that is, the non-grounded portion, is exposed, which poses a problem in that noise radiation may occur and cause damage to other nearby circuits.

SUMMARY OF THE INVENTION An object of the present invention is to provide a compact composite noise filter that improves the conventional problems.

Means for Solving the Problems In order to solve the above-mentioned problems, the composite noise filter of the present invention inserts lead wires of input/output terminals into a cylindrical conductor having an external electrode and an internal electrode, and bends the lead wires. It is inserted into a ferrite core with multiple through holes, the external electrode of the cylindrical dielectric material is electrically connected to the ground lead wire, and the external side of the magnetic material is coated with a conductive material to form a ground electrode. did.

A T-type filter can be constructed with one working cylindrical dielectric and one ferrite core, and the number of parts can be reduced and the overall shape can be made smaller.

Embodiment FIG. 1 shows the external appearance of the embodiment, FIG. 2 shows its sectional view, and FIG. 3 shows its equivalent circuit.

The lead wires 11 and 12 of the input/output terminals are passed through the cylindrical dielectric 13 and connected to the internal electrodes 14 of the cylindrical dielectric 13 and electrically connected to the internal electrodes 16 of the ferrite core 15. Furthermore, the ground terminal 17 is electrically connected to the cylindrical dielectric 13 and the external electrode 18 of the ferrite core 15 . In the equivalent circuit shown in FIG.
It is a bypass capacitor consisting of. 22 is an equivalent circuit composed of the specific resistance and distributed capacitance of the ferrite core 15, but when Ni--Zn ferrite is used, the specific resistance is large and the distributed capacitance is small, so it can be ignored. Each electrode 14, 16, 18 is formed using a ferrite core made of a material having a low specific resistance, such as Ag or Cu. Earth terminal 1
Solder is used for the connection between 7 and the external electrode 23 of the cylindrical dielectric 13 and the connection between the ground terminal 17 and the external electrode 18 of the ferrite core 15. As an example of the cylindrical dielectric body 13, as in the conventional example, the relative dielectric constant Σ-3000, the cylindrical wall thickness is 35 mm, and the capacitance C=1000 (pF). Furthermore, if the outer diameter r2 (-), inner diameter rl (輔), and cylinder length of the cylindrical dielectric 13 are L (mm), C=24.1 (ΣL
/log(r2/rl))(pF), r2=1.8(
+nm), rl=1.1 (mm), L=3 (mm
) is obtained, and even if the ferrite core 15 is combined with this shape, it becomes smaller than the conventional shape.

Effects of the Invention As is clear from the above explanation, the composite noise filter of the present invention has a cylindrical dielectric inner electrode and a magnetic inner electrode connected to the human power and output lead wires, and a cylindrical dielectric outer electrode. Since a ground lead wire is provided that is connected to the electrode and the external double positive of the magnetic material, the following effects can be obtained.

The number of parts used can be reduced to two, one cylindrical capacitor and one ferrite core.

Furthermore, it is possible to reduce the size of the device, thereby increasing the mounting density.

Furthermore, since the external electrode of both the cylindrical capacitor and the ferrite core is on the ground side, there is little noise radiation and there is little risk of interference with nearby circuit components.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of the composite noise filter of the present invention, Fig. 2 is a cross-sectional view of the same, Fig. 3 is an equivalent circuit diagram, and Fig. 4 is an equivalent circuit diagram.
The figure is a conventional perspective view, and FIG. 5 is an equivalent circuit diagram. 11... Input terminal 12... Output terminal 13... Cylindrical dielectric material 14... Internal electrode 15... Magnetic material 16... Internal electrode 17... Earth terminal 18...Name of external electrode agent Patent attorney Toshio Nakao and one other personff
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Claims (2)

[Claims] (1) A cylindrical dielectric body is provided with an external electrode and an internal electrode, a lead wire connected to an input terminal and an output terminal is connected to the internal electrode of the cylindrical dielectric body, and a magnetic body is provided with an external electrode and a plurality of internal electrodes. A composite noise filter characterized in that an internal electrode is provided, the lead wire is connected to the internal electrode of the magnetic material, and a ground lead wire is connected to the external electrode of the cylindrical dielectric material and the external electrode of the magnetic material. . (2) The composite noise filter according to claim 1, characterized in that Ni--Zn ferrite is used as the magnetic material.