JP2000188221A - Shielding winding whose center tap is connected with ground - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shielding winding which is suitable for mass-production and can fully obtain the effect of electrostatic shielding. SOLUTION: Two shielding windings 2, 3 are arranged between a primary coil P and a secondary coil S. The polarities of the shielding windings are different, one terminal 2b of the shielding winding 2 is connected with a ground, and the other terminal 2a is set unconnected. In the shielding winding 3, a coil terminal 3a is connected with the ground, and the other terminal 3b is set unconnected. The two coils 2, 3 make a shielding winding 1, where common ground is used as a center tap.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil component such as a transformer and a choke coil mounted on various electronic devices.

[0002]

2. Description of the Related Art A transformer is a typical example of a coil component mounted on various electronic devices. Transformers are used as conversion elements for electric power, electric signals, and the like, and have various forms. There is an electrostatic shield for the purpose of increasing efficiency or reducing noise as a transformer. This electrostatic shield prevents a noise component caused by a capacitor between a primary coil and a secondary coil from passing between the coils of a transformer including a primary coil and a secondary coil.

FIG. 8 shows a transformer provided with an electrostatic shield, in which a shield 11 made of a copper plate is wound between a primary coil P and a secondary coil S, one end of which is connected to ground, and the other end is not connected. And With this copper plate shield 11, 1
The noise component passing between the secondary coil P and the secondary coil S can be easily released to the ground. However,
The electrostatic shield made of a copper plate has a large coil portion, and has become expensive due to insulation of the surface of the copper plate, connection of a lead wire to the ground of the copper plate, and the like.

As an inexpensive alternative to the copper plate, there is a shield winding shown in FIG. The shield winding 12 is formed by winding a single-layer winding of a copper wire between the primary coil P and the secondary coil S, and has one end connected to the ground and the other end not connected to the same as the copper plate shield. With a coil structure, it was able to handle small coil components.

[0005]

The above-mentioned shield winding 1
No. 2 was inferior to the copper plate shield 11 in the shielding performance. The cause will be described with reference to FIG.
10A is a schematic diagram illustrating a coil portion of a transformer using a copper plate shield 11 and FIG. In the case of the copper plate shield 11, the noise component flowing from the position c is linearly transmitted to the ground through the copper plate, whereas in the case of the shield winding 12, the noise component flowing from the position d is Shield winding 1 wound around core
It flows through 2 and goes to the ground. Even if a noise component flows in the copper plate shield 11, only a slight magnetic flux is generated for the core. On the other hand, the shield winding 12 is wound around the core and the noise component flows. A large magnetic flux was generated in the core, which significantly deteriorated the shielding performance as noise removal. The present invention provides a shield winding capable of obtaining an electrostatic shielding effect equivalent to that of a copper plate shield even with a winding structure.

[0006]

SUMMARY OF THE INVENTION The present invention provides a primary coil,
In a shield winding applied to a winding part including a secondary coil, a bobbin around which the secondary coil is wound, and a core, the shield winding is configured by at least two or more coils,
The polarity of half of the coils is reversed, and each of the coils has one end connected to ground and the other end unconnected, and
It is a shield winding for connecting the center tap wound between the secondary coil and the secondary coil to the ground.

Further, the shield winding of the present invention uses two coils of different polarities, one of which is connected to the ground and the other is not connected, as at least one set of coils. This is a shield winding for connecting a center tap formed of a coil to the ground.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a shield winding according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic circuit diagram of a transformer using a shield winding for connecting a center tap to the ground according to the present invention. FIG. 2 is a schematic cross-sectional view of a transformer using a shield winding for connecting a center tap to the ground according to the present invention.

The shield winding of the present invention comprises two shield windings 2, 3 between a primary coil P and a secondary coil S, as shown in FIG. One terminal 2b of the line 2 was connected to the ground, and the other terminal 2a was not connected. In the shield winding 3, the coil terminal 3a is connected to the ground, and the other terminal 3b is not connected. The two coils 2 and 3 form a shield winding 1 having a ground connection as a center tap.

When a noise component passing between the primary coil P and the secondary coil S flows from a and b of the shield windings 2 and 3, a magnetic flux φ2 due to the noise component flows into the core 4 around which the shield winding 2 is wound. Occurs. Also, since the shield winding 3 is wound around the core 4, a magnetic flux φ generated by the shield winding 2 due to a noise component flowing through the shield winding 3.
A magnetic flux φ3 opposite to the direction 2 is generated. That is, the magnetic fluxes φ2 and φ3 generated by the shield windings 2 and 3 due to the noise components are magnetic fluxes generated in opposite directions, and therefore cancel each other out, so that the deterioration of the shield effect of the windings can be reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an embodiment of the present invention, the effect of the present invention in a communication transformer will be described below. This communication transformer is a transformer mounted on a data transmitting / receiving circuit,
This product emphasizes high inductance and low transmission loss. In examining the effect of the electrostatic shield of the present invention, as a comparative example, one using a copper plate shield and one using a conventional shield winding were compared under the same specifications.

The core is made of Mn to obtain high inductance.
In this embodiment, a Zn-based ferrite material is used, and in this embodiment, E is made of GP-10 (μi = 7000) manufactured by Hitachi Metals, Ltd.
The PC13 shape was used. The coil has a coil connection diagram shown in FIG. 3 and has an inductance of 22 mH or more between the coils. The external dimensions of this transformer are 14 × 14 × 8.5 t (mm). FIG.
FIG. 1 shows the shield 5 of the present invention, and FIG.
The conventional shield winding was implemented in the form shown in FIG.

The characteristic comparison is based on one of the evaluation methods of the shielding effect.
Comparative measurement was made using the longitudinal current unbalanced attenuation characteristic. The longitudinal current unbalanced decay characteristics were measured using an impedance / gain phase analyzer 4194A (manufactured by Japan HP) as shown in FIG.
The evaluation circuit was used. FIG. 5 is a longitudinal current unbalanced attenuation characteristic diagram of a transformer using a shield winding for connecting the center tap to the ground according to the present invention, and a similar longitudinal current unbalanced attenuation characteristic diagram was obtained with the conventional shielding method. . Table 1
Fig. 3 shows the amount of longitudinal current unbalance attenuation by each electrostatic shield method.

[0014]

[Table 1]

The shield winding of the present invention was able to obtain the same amount of longitudinal current unbalance attenuation as the copper plate shield. The conventional shield winding shows the same attenuation as the copper plate shield at 10 kHz, but the attenuation decreases as the frequency increases, and the shielding effect is clearly degraded.

In the above embodiment, the shield winding of the present invention is provided between the primary coil P and the secondary coil S.
In the case where the coil shown in FIG. 6 is a transformer having a sandwich structure, as shown in the figure, shield windings 6 and 7 are provided between the primary coil P and the secondary coil S, and one end of the coil is connected to the ground. Thus, the effect of the present invention can be obtained.

Further, in the case of a coil having a sandwich structure as shown in FIG. 7, one shield winding according to the present invention may be arranged between each coil winding layer. In this case, 2
Although the magnetic flux is canceled by the noise component generated from the two shield windings 8 and 9, the magnetic flux generated by the remaining shield winding 10 is generated in the core, but the noise can be reduced by the shield winding of the present invention. .

In order to obtain the effect of the shield winding of the present invention, it is preferable to use two sets of shield windings having different polarities. In FIG.
The effect of the shield can be improved by changing to a set of shield windings. Further, by winding the two shield windings adjacent to each other, it is possible to obtain a further shielding effect by minimizing a difference in resistance and the like of the windings.

[0018]

According to the present invention, workability, prevention of coil section enlargement, and noise of small coil parts are achieved by using an electrostatic shield applied to a coil part such as a transformer as a shield winding for connecting a center tap to the ground. It is possible to take a countermeasure and an inexpensive shield countermeasure, and it is possible to obtain a shielding effect equivalent to a copper plate shield.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram of a transformer using a shield winding for connecting a center tap to the ground according to the present invention.

FIG. 2 is a schematic cross-sectional view of a transformer using a shield winding for connecting a center tap to the ground according to the present invention.

FIG. 3 is a wiring diagram of a transformer used for measurement of longitudinal current unbalance attenuation.

FIG. 4 is a circuit diagram for evaluating a longitudinal current unbalanced attenuation characteristic.

FIG. 5 is a longitudinal current unbalanced attenuation characteristic diagram of a transformer using a shield winding for connecting a center tap to the ground according to the present invention.

FIG. 6 shows another embodiment of a transformer using a shield winding for connecting the center tap to the ground according to the present invention.

FIG. 7 shows another embodiment of the transformer using the shield winding for connecting the center tap to the ground according to the present invention.

FIG. 8 is a schematic circuit diagram of a transformer using a conventional copper plate shield.

FIG. 9 is a schematic circuit diagram of a transformer using a conventional shield winding.

FIG. 10 is an explanatory diagram of a conventional shielding method.

[Explanation of symbols]

 1 shield winding for connecting the center tap to the ground 2 shield winding 2a, 2b coil end 3 shield winding 3a, 3b coil end

Claims (2)

[Claims] 1. A shield winding applied to a winding component comprising a primary coil, a secondary coil, and a bobbin and a core around which the coil is wound, wherein the shield winding comprises at least two or more coils. And each of the coils has one end connected to the ground and the other end unconnected, and each of the primary coils has a reverse polarity. A shield winding for connecting a center tap to ground, which is wound between secondary coils. 2. The shield winding, wherein one coil end is connected to the ground and the other coil end is not connected, two coils having different polarities are used as one set, and at least one or more sets of the coils are used. 2. The method according to claim 1, wherein
A shield winding that connects the described center tap to ground.