JP3316008B2 - Transformers and power supplies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer and a power supply device using the transformer, and more particularly to an improvement in performance and a reduction in thickness.

[0002]

2. Description of the Related Art For the purpose of improving the coupling between primary and secondary coils by reducing the thickness of a transformer and reducing leakage magnetic flux, as disclosed in Japanese Patent Application Laid-Open No. 60-715, for example,
There has been proposed an insulating plate in which magnetic powder is applied to primary and secondary coils formed in a plane spiral shape on both surfaces.

[0003] For example, Japanese Patent Application Laid-Open No. 61-42109 discloses a structure in which planar printed coils are stacked to reduce the thickness of a transformer.

[0004]

In the prior art described above, the primary and secondary coils of the transformer are laminated with an insulating plate interposed therebetween, so that the overall thickness of the transformer is primary, secondary conductor, insulating substrate,
The total thickness of the magnetic material layer was reached, and there was a limit to the reduction in thickness.

Also, since the distance between the primary and secondary conductors is increased by the thickness of the insulating substrate, the leakage magnetic flux increases, and the thickness of the magnetic layer must be increased in order to prevent the magnetic flux from dissipating. Was.

[0006] Further, a transformer having stacked planar printed coils has a problem that the stray capacitance between the primary and secondary coils increases.

SUMMARY OF THE INVENTION An object of the present invention is to realize a transformer having a large coupling coefficient between primary and secondary, a small leakage magnetic flux and a small stray capacitance, and a small thickness.

[0008]

According to the present invention, in order to achieve the above object, a plurality of conductors with insulating coating are arranged close to one plane, a part of which is used as a primary coil and another part is used as a secondary coil. In addition, a configuration was adopted in which a magnetic material covering both of them was provided.

[0009]

Since a plurality of insulated conductors are arranged close to each other on one plane, magnetic coupling occurs between adjacent conductors and leakage magnetic flux can be reduced.

The thickness of the entire transformer is obtained by adding the thickness of the magnetic shield layer to the diameter of the conductor, and the thickness can be reduced.

The higher the frequency of the transformer of this construction, the higher the current flowing in the primary and secondary conductors is brought to the surface by the skin effect, so that the coupling between the adjacent primary and secondary conductors is improved and the leakage magnetic flux is reduced. .

[0012] Then, the remaining leakage magnetic flux can be prevented from dissipating to the outside by the magnetic material disposed over the primary and secondary conductors.

If the cross section of the conductor is substantially circular, the area of the adjacent conductor facing each other at a close distance becomes small, and the capacitance can be reduced.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the overall configuration of a transformer according to the present invention.

As an example, the transformer 1 has two insulated wires 11 and 12 arranged side by side and spirally wound together so as not to intersect with each other.
It is configured by covering with 1.

This embodiment will be described in more detail with reference to a sectional view.

FIG. 2 shows a cross section including all the center lines of the two insulated wires 11 and 12 spirally wound on the same plane in FIG. 1, and FIG. 3 is a sectional view taken along the line III-III 'of FIG.
Shown in

The operation of the transformer of this embodiment will be described with reference to FIG.

The alternating current flowing through the insulated wires 11 and 12 is converted by the skin action into regions 11a and 12 near the skin of the wires.
Concentrate on a.

When the electric wire 11 is on the primary side and the electric wire 12 is on the secondary side, the magnetic flux φ ₁ generated by the current flowing through the electric wire 11 is chained to the electric wire 12 near the portion 13 where the electric wires 11 and 12 are in contact with each other. And the primary side and the secondary side are magnetically coupled.

The higher the frequency, the stronger the skin effect and the more the current is brought to the surface, so that the above coupling becomes larger.

In this embodiment, as shown in FIG. 5, a part φ _L of the magnetic flux generated by the current flowing through the primary electric wire 11 flows through the magnetic shield 21 and the primary electric wire is also linked with the secondary electric wire 12 to link the primary electric wire. , The secondary side is magnetically coupled.

In a transformer generally used at a commercial frequency, coupling between the primary and secondary by the magnetic flux φ _L in the magnetic shield 21 is mainly performed. However, in the high frequency transformer according to the present embodiment, the primary and secondary electric wires are connected. The coupling mainly by the magnetic flux directly interlinking the magnetic fluxes 11 and 12 and the coupling by the magnetic flux φ _L in the magnetic shield 21 are added to this.
The coupling coefficient between the quadratures is greatly improved.

Normally, the magnetic permeability of the magnetic material constituting the magnetic shield decreases as the frequency increases. However, as shown in this embodiment, the magnetic shield 21 is not coupled by the magnetic flux directly linked to the primary and secondary wires 11 and 12. The effect of the decrease in magnetic permeability is small. Conversely, as the frequency increases, the skin effect becomes more pronounced and the coupling improves.

One of the features of the transformer of the present invention is that the leakage magnetic flux is small.

Since the primary and secondary electric wires 11 and 12 are arranged close to each other, the leakage magnetic flux is small by itself, but the entire winding body of the electric wires 11 and 12 is covered with the magnetic shield. Thus, the magnetic flux radiated to the outside can be greatly reduced, and the transformer emits a small amount of magnetic noise.

FIGS. 1 to 3 show the magnetic shield 21 as the electric wire 1.
This shows an embodiment in which substantially the whole of the wound bodies 1 and 12 is covered, and the magnetic shield 21 must be cut off at the lead-out portion at the end of the electric wire.

However, since the magnetic coupling required in the present transformer does not depend so much on the magnetic shield 21, even if a part is omitted, the characteristics of the transformer are not impaired.

In the transformer of this embodiment, since the wires 11 and 12 having a substantially circular cross section are arranged side by side,
The surface area is smaller than the cross-sectional area.

Since the facing areas of the primary and secondary wires 11, 12 are also much smaller than the structure in which the flat coils are stacked, the stray capacitance between the wires 11, 12 is much smaller than that of the transformer using the flat coils. .

The thickness of the transformer of the present invention is the diameter of the larger one of the primary and secondary wires 11 and 12 (in the present embodiment, an example is shown in which both wires 11 and 12 have substantially the same thickness). And the thickness of the magnetic shield 21 is added to the thickness of the transformer, so that the primary and secondary wires can be stacked with the insulating substrate interposed therebetween, and can be significantly thinner than a transformer in which the thickness of the iron core and the magnetic shield is added.

FIG. 6 shows a modified example of the present invention, in which a hole 22 is provided at the center of a magnetic shield 21 covering a winding body of an electric wire.
An example is shown in which the inner peripheral end 14 of the wire wound in a spiral shape is drawn out from here.

FIG. 7 is a sectional view taken along the line VII-VII 'of FIG.

Although the magnetic shield 21 has a smaller sectional area of the hole 22, the magnetic flux flowing through the magnetic shield originally plays an auxiliary role of magnetic coupling and does not impair the performance of the transformer.

FIG. 6 shows an embodiment in which the hole 22 is used as a space for drawing out electric wires. However, the hole 22 can be used as a hole for inserting a screw or a fixing pin when mounting a transformer on a board.

The hole 22 does not necessarily need to be a through hole, and one end may be closed by a magnetic shield depending on the purpose.

FIG. 8 is a sectional view of a transformer according to another modification of the present invention.

Winding body 1 of primary wire 11 and secondary wire 12
This is an example in which the magnetic shield 21 covering 5, 5 'is an open magnetic path.

In general, when the magnetic path of the transformer is an open magnetic path, the leakage magnetic flux increases to deteriorate the coupling between the primary and the secondary, and the magnetic shield of the open magnetic path has a large leakage magnetic flux and the shielding effect is inferior. There's a problem.

However, in the transformer of the present invention in which the main component of the magnetic coupling depends on the magnetic flux directly linked between the primary and secondary wires 11 and 12, the magnetic flux flowing through the magnetic shield 21 itself is small. Characteristic can be obtained.

Then, as shown in FIG. 8, the primary wire 11 and the secondary wire 12 are arranged and wound in the gap 23 of the magnetic shield 21 having the outer peripheral end side as an open magnetic path, so that the wires 11 and 12 are not overlapped or disturbed. It is possible to easily configure the wire winding body 15 that is not aligned.

FIG. 9 is a sectional view of a transformer according to still another modification of the present invention.

This is an example in which both surfaces and outer peripheries of the wire winding bodies 15 and 15 ′ of the primary wire 11 and the secondary wire 12 are covered with a magnetic shield 21.

In this example, the magnetic flux leaking to the outside is shielded, but the magnetic path of the magnetic flux flowing through the magnetic shield 21 and contributing to the primary and secondary coupling is an open magnetic path.

However, in the transformer of the present invention, as in the embodiment of FIG. 8, the magnetic flux flowing through the magnetic shield 21 itself is small, so that a predetermined characteristic can be obtained even as an open magnetic circuit as described above.

According to this configuration, the wire winding body 15
Since there is no need to provide a space through which the magnetic shield 21 penetrates inside 16, there is an effect that the whole can be reduced in size.

In the above embodiment, the magnetic shield 21
May be constituted by a combination of a magnetic plate, for example, a ferrite plate 24 and a ferrite molded body 25 as shown in the cross-sectional view of FIG. 10, and as a further modified example of this case, the ferrite plate 24 is It is also possible to mount a circuit component group 31 such as other switching elements and use it as a substrate constituting the power supply device 32 and the like, which has the effect of making the entire device thinner.

As shown in FIG. 11, both sides of the winding bodies 15, 15 'of the primary electric wire 11 and the secondary electric wire 12 are
Even in the configuration sandwiched between 4, 24 ', the effects of improving the coupling between the primary and secondary and shielding the leakage magnetic flux can be obtained.

For example, the power supply device 32 and the like can be formed by mounting the transformer 1 and the other circuit component groups 31 on one ferrite plate 24, which has the effect of reducing the overall thickness of the device.

An application example of the present invention will be described with reference to FIG.

Wound body 1 of primary wire 11 and secondary wire 12
5, 15 'are ferrite plates 24 as an example of a magnetic thin plate.
, And the surface thereof is coated with a resin containing magnetic particles, for example, a ferrite paste 27 in which ferrite powder and a resin are mixed together as an example, and solidified.

Then, these components can be mounted on the circuit board 26 together with components such as other switching elements to constitute a power supply device or the like.

According to this configuration, the ferrite plate 24 and the ferrite paste 27 function as a magnetic shield, and effectively act to improve the coupling between the primary electric wire 11 and the secondary electric wire 12 and shield the leakage magnetic flux.

The effect of coating with magnetic particles is that a magnetic layer can be formed in close contact with an uneven surface such as the surface of a wire wound body.

Generally, the magnetic permeability of ferrite powder is about several tens, which is considerably smaller than that of a general block material.
The transformer of the present invention, which depends on the magnetic flux directly linking the primary and secondary wires with the main component of the magnetic coupling, works sufficiently effectively.

FIG. 13 shows a modification of the embodiment shown in FIG.

This is an embodiment in which the ferrite plate 24 for fixing the winding bodies 15, 15 'in which the primary electric wire 11 and the secondary electric wire 12 are wound side by side is shared with a circuit board.

According to this structure, the total height of the substrate and the transformer can be reduced, and the power supply device incorporating the transformer can be made thinner.

FIG. 14 shows still another modification.

The windings 15 and 15 ′ in which the primary wire 11 and the secondary wire 12 are wound side by side are covered with a magnetic shield made of only the ferrite paste 27 to form a transformer.

According to the ferrite paste, since a magnetic layer much thinner than a flat plate can be formed, there is an effect that the thickness of the transformer can be further reduced.

[0063]

According to the present invention, as described above, a plurality of conductors with insulating coating are arranged in close proximity on one plane, a part of which is used as a primary wire, and the other is used as a secondary wire.
In addition, since a configuration was adopted in which a magnetic material covering both was adopted,
Magnetic coupling occurs between the adjacent primary and secondary electric wires, so that the leakage magnetic flux can be reduced, and the remaining leakage magnetic flux can be prevented from being radiated to the outside by the magnetic material disposed over the primary and secondary conductors.

The thickness of the entire transformer is a value obtained by adding the thickness of the magnetic shield layer to the diameter of the conductor, and the thickness can be reduced.

As a result, it is possible to realize a transformer having good coupling between the primary and secondary, a small leakage magnetic flux and a small stray capacitance, and a small thickness.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a transformer according to an embodiment of the present invention, in which two conductors wound in a spiral shape are covered with a magnetic shield.

FIG. 2 is a cross-sectional plan view of the embodiment shown in FIG.

FIG. 3 is a sectional view taken along the line III-III ′ of the embodiment shown in FIG. 1;

FIG. 4 is a conceptual diagram illustrating an example of a flow of a magnetic flux in the embodiment shown in FIG.

FIG. 5 is a conceptual diagram illustrating another example of the flow of magnetic flux in the embodiment shown in FIG.

FIG. 6 is an external view of a transformer having a hole in a magnetic shield according to a modified example of the present invention.

FIG. 7 is a sectional view taken along the line VII-VII 'of the embodiment shown in FIG.

FIG. 8 is a cross-sectional view of a transformer in which a magnetic shield has an open magnetic path according to a modification of the present invention.

FIG. 9 is a cross-sectional view of a transformer according to a modification of the present invention in which a magnetic shield inside a spiral wire winding body is omitted.

FIG. 10 is a cross-sectional view of a transformer using a magnetic flat plate also serving as a power supply substrate as a part of a magnetic shield according to an application example of the present invention.

FIG. 11 is a cross-sectional view of a transformer in which a magnetic shield is constituted by two magnetic flat plates which also serve as a power supply substrate, according to an application of the present invention;

FIG. 12 is a cross-sectional view of a transformer in which a part of a magnetic shield is made of a magnetic paste according to an application example of the present invention.

FIG. 13 is a cross-sectional view of a transformer in which a magnetic shield is made up of a magnetic plate and a magnetic paste, partly serving as a power supply substrate, of an application example of the present invention.

FIG. 14 is a cross-sectional view of a transformer according to an application example of the present invention, in which a magnetic shield is formed using only a magnetic paste.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transformer, 11, 12 ... Insulated wire, 15,1
5 ': Electric wire wound body, 21: Magnetic shield, 22: Hole, 24, 24': Ferrite plate, 25: Ferrite molded body, 26: Circuit board, 27: Ferrite paste, 3
1 ... circuit part group, 32 ... power unit, phi _1, phi _L ... flux.

Continuing from the front page (72) Inventor Kenichi Onda 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Tadashi Takahashi 7-1-1, Omika-cho, Hitachi City, Ibaraki Stock Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Reiko Kanoda 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Hitachi Research Laboratory Co., Ltd. (72) Inventor Hideaki Horie 7-1, Omika-cho, Hitachi City, Ibaraki Prefecture No. 1 Hitachi, Ltd. Hitachi Research Laboratory (56) References JP-A-3-82104 (JP, A) JP-A-60-715 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) H01F 27/32 H01F 27/36 H01F 27/28

Claims (4)

(57) [Claims] (1) A state in which they are in contact on the same plane via an insulating member.
A part of a plurality of conductors having a substantially circular cross section, which are wound and arranged in a state, are formed as one circuit and the other as another circuit, and the conductor winding body is covered with a magnetic shield. A transformer characterized by that: 2. A state of contact on the same plane via an insulating member.
Wound in condition, are arranged, one circuit part of the plurality of conductors of cross-section substantially circular, and the other with another circuit, magnetic flat magnetic shield to be <br/> covering the conductor winding body A transformer characterized by comprising circuit components mounted on its magnetic flat plate. 3. Oite to claim 1, the magnetic shield and the magnetic powder coating, composed by fixing the transformer. 4. A power supply device using the transformer according to claim 1.