JPS646589Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a noise filter used in a circuit that effectively removes electrical interference waves (hereinafter referred to as noise).

As a circuit for removing noise, for example, an LC noise prevention filter circuit is used. This noise prevention filter circuit is constructed by inserting a capacitor between the signal line and the ground, and by inserting, for example, a common mode choke coil for a noise filter in series with the signal line.

By the way, in the case of a configuration in which two common mode choke coils (hereinafter abbreviated as coils) are connected in series to the signal line, the diameter of the link-shaped magnetic core and the coil should be adjusted to meet the demand for miniaturization of products. Therefore, in order to obtain a predetermined inductance, it was necessary to wind the coil around the magnetic core in multiple layers. As shown in FIG. 1, the noise filter that has been conventionally implemented as a multi-layer winding is as shown in FIG.
After winding the coil 2 from 1 to the winding end portion 1c, the coil 2 is further folded back and wound to the middle portion 1b, thereby forming a sparse portion 2A and a dense portion 2B in the winding layer of the coil, thereby forming a first common mode winding coil. (hereinafter abbreviated as the first coil) 3 is formed, while a second common mode choke coil (hereinafter abbreviated as the second coil) 13 is also wound with a coil 12 around a ring-shaped magnetic core 11 in the same manner as described above. The dense portion 2B of the first coil 3 and the sparse portion 12A of the second coil 13 are formed on the side facing the first coil 3 on the left side of the figure and the second coil 13 on the right side of the figure that have been formed in this way. In the installed state, one ends of the coils 2 and 12 were connected to each other, and a capacitor 4 was interposed. Incidentally, FIG. 2 is an example of the circuit shown in FIG. 1.

However, as described above, the dense portion 2B of the coil winding layer in the first coil 3 is in the second coil 13.
, the leakage magnetic flux M from the second coil 13 is electromagnetically coupled to the dense portion 2B of the first coil 3. However, it is known that this leakage magnetic flux increases as the frequency increases. Therefore, the first coil 3
Due to the leakage magnetic flux M electromagnetically coupled to the first coil 3
It has been found that the original inductor effect of the inductor deteriorates at high frequencies, reducing the noise attenuation effect.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a noise filter that prevents deterioration of the noise attenuation effect without significantly changing the conventional structure.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a schematic perspective view showing an embodiment of the present invention. In FIG. 3, reference numerals 21 and 31 indicate ring-shaped magnetic cores made of a high magnetic permeability material such as ferrite or permalloy, and reference numerals 22 and 32 indicate the winding start portions of the magnetic cores 21 and 31, respectively. 21
a, 31a to the winding end portions 21c, 31c, and then further folded back to intermediate portions 21b, 31b.
This is a coil wound up to . 23 and 33 indicate the coils 22 and 33 attached to the magnetic cores 21 and 31 as described above.
32 into the wound layer by winding the sparse portion 22
A, 32A and dense portions 22B, 32B are formed in the first common mode chiyoke coil (hereinafter abbreviated as the first coil) and the second common mode chiyoke coil (hereinafter abbreviated as the second coil). The coil winding layers on the facing side of the first coil 23 and the second coil 33 are both sparse portions 22A and 32.
The first coil 23 and the second coil 33 are connected in series by connecting one ends of the coils 22 and 32 so as to form A. In addition, in the figure, 44 is the first
This is a capacitor inserted between the connection point between the coil 23 and the second coil 33 and the ground.

Incidentally, FIG. 4 shows a filter circuit for noise prevention according to the present invention.

As is clear from the above, in the noise filter of the present invention, in the first coil 23 and the second coil 33 arranged in series, the sparse portions 22A and 32A of the coil winding layer are located on opposite sides, and the first coil 23 and the second coil 33 are arranged in series. Since the dense portion 22B of the second coil 33 is configured to have a distance, the electromagnetic coupling caused by the leakage magnetic flux M from the second coil 33 jumping into the dense portion 22B of the first coil 23 is reduced. Even at high frequencies, the characteristics of the first coil 23 do not deteriorate.

FIG. 5 is a graph showing the high frequency attenuation characteristics of the noise filter of the present invention, which shows that the characteristics of the noise filter of the present invention are compared to the characteristics (shown by the dotted line) A when a conventional noise filter is used. It can be seen that B (shown by a solid line) is considerably improved.

Note that the noise filter of the present invention is not limited to the above-mentioned embodiments, and can be modified and implemented without changing the gist of the present invention. For example, the first coil 2
3 and the second coil 33 do not necessarily need to have the same number of turns, and it is sufficient that sparse portions and dense portions are formed in the winding layer of the coil.

As detailed above, the noise filter of the present invention can contribute to improving high frequency attenuation characteristics by assembling the connection between common mode choke coils to reduce electromagnetic coupling of leakage magnetic flux. be.

[Brief explanation of the drawing]

Figure 1 is a schematic perspective view showing a conventional noise filter, Figure 2 is an example of the circuit in Figure 1,
Fig. 3 is a schematic perspective view showing an embodiment of the noise filter of the invention, Fig. 4 is a circuit example of the noise filter of the invention, and Fig. 5 is a graph showing high frequency attenuation characteristics of the noise filter of the invention. be. 21, 31...Magnetic core, 21a, 31a... Winding start part, 21b, 31b... Intermediate part, 21c, 3
1c... End of winding, 22, 32... Coil, 2
2A, 32A... sparse portion, 22B, 32B... dense portion, 23... first common mode chiyok coil, 33... second common mode chiyok coil,
44... Capacitor.

Claims (1)

[Scope of utility model registration request] A first common mode chip is formed by forming a sparse portion and a dense portion in the winding layer of the coil by winding the coil from the winding start part to the winding end part of a ring-shaped magnetic core, and then folding it back and winding it to the middle part. In a noise filter in which one end of each coil wire of a yoke coil and a second common mode yoke coil formed by winding a coil around a ring-shaped magnetic core in the same manner as described above is connected, and a capacitor is interposed, the first common A noise filter characterized in that the coil winding layers on the opposite side of the connection point between the mode chioke coil and the second common mode chiyoke coil are sparse.