JPH05283247A - Transformer - Google Patents

Abstract

PURPOSE:To enhance the reliability of a transformer and to increase its life by improving insulating performance between a primary coil and a secondary coil. CONSTITUTION:A transformer has a primary coil 6 shunt-wound in windings 5a, 5b of a bobbin 2 for a primary coil formed with the two windings 5a, 5b via a partition wall 4. A bobbin 3 for a secondary coil is formed of molding resin M for resin-sealing the coil 6. The secondary coil 13 is wound on a winding 5c for the secondary coil at the bobbin 3 for the secondary coil formed at the side of the bobbin 2 for the primary coil, and the coil 13 is further covered with a heat resistant film 14. The transformer is formed by inserting a magnetic core 1 coaxially into a through hole 8 of the bobbin 2 for the primary coil and a through hole 9 of the bobbin 3 for the secondary coil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency transformer such as a ferrite transformer used for a switching power supply transformer.

[0002]

2. Description of the Related Art As shown in FIG. 12, a conventional transformer used for a switching power supply has two partition walls 21a.
And 21b three windings 22a, 22b and 22c
And a coaxial magnetic core 2 inserted into a through hole 24 formed in the axial direction of the bobbin 23.
5 and. Then, for example, the first and second bobbins 23
The primary coil 26 is divided and wound around the second winding portions 22a and 22b, and the secondary coil 27 is wound around the third winding portion 22c, thereby forming a transformer.
The equivalent circuit of this transformer is shown in FIG.

However, in the case of the above construction, it is necessary to provide a space creeping distance a between the primary coil 26 and the secondary coil 27 in view of safety standards, and the partition wall 21b between the primary coil 26 and the secondary coil 27 is provided. Must have a predetermined insulation thickness b. In numerical terms, the space creepage distance a is 8 m.
The insulating thickness b is about 2 mm. In particular, there is a problem that the height H1 of the bobbin 23 increases due to the above-mentioned space creepage distance a, and the size of the transformer itself increases.

Therefore, conventionally, as shown in FIGS. 14 and 15, the primary coil 26 and the secondary coil 27 wound around the bobbin 23 are resin-sealed with a molding resin M to form a transformer. ing. According to this configuration, it is not necessary to provide the space creepage distance a between the primary coil 26 and the secondary coil 27, and the height H2 of the bobbin 23 can be made smaller than the height H1 of the bobbin 23 shown in FIG. The size of the transformer itself can be reduced.

[0005]

By the way, in the transformer shown in FIG. 14 and FIG. 15, as the material of the bobbin 23, the bobbin 23 is more thermally deformed than the mold resin M so that the bobbin 23 is not deformed by the molding temperature of the mold resin M. High temperature resins (generally thermosetting resins) must be used.

Therefore, the bobbin 23 and the mold resin M must be different materials, and the interface between the bobbin 23 and the mold resin M is very unstable. Become. Therefore, as shown in FIG. 16, during winding of the molding resin M, or due to changes in the environment after molding or changes with time, between the windings that should have been sealed by the molding resin M, especially the primary coil 26 and the secondary coil that need insulation. Next coil 2
A minute void 28 is easily formed on the peripheral surface of the partition wall 21b between the seven. The gap 28 is formed by the primary coil 26 and the secondary coil 27.
Insulation performance between the two deteriorates remarkably, which causes a problem of reducing the reliability and life of the transformer.

[0007] In the present situation, the resin combination currently used is one that is completely incompatible and has a very good compatibility with properties such as coefficient of thermal expansion and water absorption. In this case, it is very difficult to perform quality control and quality assurance for interfacial peeling in terms of molding condition management and environmental reliability.

The present invention has been made in view of the above problems. An object of the present invention is to improve the insulation performance between the primary coil and the secondary coil, and to improve the reliability of the transformer and It is to provide a transformer capable of achieving a long life.

[0009]

According to the present invention, a bobbin 2 having a partition wall 4 is disposed on a coaxial magnetic core 1, and the bobbin 2 is provided with the bobbin 2.
Winding parts 5a to 5c partitioned by the partition wall 4 of
In addition, the primary coil 6 and the secondary coil 13 are separated and wound, respectively, and the primary coil 6 and the secondary coil 13 are further wound.
However, in the transformer resin-sealed with the molding material M, one of the primary coil 6 and the secondary coil 13 (for example, the primary coil 6) is sealed with the molding material M and the other coil (for example, the secondary coil 13). The bobbin 3 of the next coil 13) is integrally formed of the same material.

[0010]

According to the above-mentioned structure of the present invention, the molding material M for resin-sealing one coil (for example, the primary coil 6).
Since the bobbin 3 of the other coil (for example, the secondary coil 13) is integrally formed of the same material, the one coil 6 is sealed in the mold material M.
The other coil 13 is wound on the bobbin 3 formed of the same molding material M.

Therefore, even if a void is formed at the interface between the bobbin 2 around which one of the coils 6 is wound and the molding material M due to changes in the environment or after the molding of the molding material M or after molding. The insulation between the one coil 6 and the other coil 13 can be sufficiently ensured, and the reliability and life of the transformer can be improved.

[0012]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a perspective view showing a transformer for a switching power supply according to this embodiment, and FIG. 2 is a vertical sectional view thereof.

As shown, this transformer has a coaxial magnetic core 1, a primary coil bobbin 2 and a secondary coil bobbin 3. The bobbin 2 for the primary coil is a multi-section type and is made of a thermosetting resin, for example, an unsaturated polyester resin, and the partition wall 4 is integrally formed at the axial center thereof. By this partition 4, the bobbin 2
Two winding parts 5a and 5b are formed in the coil, and the primary coil 6 made of, for example, an insulation-coated copper wire is separately wound into the two winding parts 5a and 5b. In the figure, 7
Indicates an external terminal pin.

The bobbin 3 for the secondary coil is integrally formed of the molding resin M for sealing the primary coil 6, and the winding portion 5c for the secondary coil is formed next to the bobbin 2 for the primary coil. Is molded. Therefore, the magnetic core 1 includes the through hole 8 of the primary coil bobbin 2 and the secondary coil bobbin 3.
Inserted through the through hole 9. As the material of the bobbin 3 for the secondary coil, a thermosetting resin, for example, an unsaturated polyester resin, is used as in the bobbin 2 for the primary coil. In addition, specifically, CE5100 (trade name: Matsushita Electric Works) was used as the bobbin 2 for the primary coil, and CE2870 (trade name: Matsushita Electric Works) was used as the bobbin 3 for the secondary coil.

Next, the method of forming the bobbin 3 for the secondary coil will be described with reference to FIG. 3. As shown in the drawing, of the first and second molds 11L and 11R moving in the left-right direction, The primary coil bobbin 2 around which the primary coil 6 is wound is attached to the first die 11L, and in this state, the second die 11R is moved to the first die 11L side and the ends thereof are brought into contact with each other. Let

After that, the first and second molds 11L and 1L
Upper mold 12U and lower mold 12B moving up and down in 1R
Are brought close to each other to form a cavity along the shape of the bobbin 3 for the secondary coil with the first and second molds 11L and 11R, the upper mold 11U and the lower mold 12B. After that, a resin M is injected into the cavity through a runner (not shown) and a gate G to mold the secondary coil bobbin 3 made of the mold resin M. At this time, the primary coil 6 wound around the primary coil bobbin 2 is resin-sealed by the portion of the secondary coil bobbin 3 excluding the winding portion 5c.

Then, as shown in FIG. 2, a secondary coil 13 made of, for example, an insulating coated copper wire is wound around the winding portion 5c of the secondary coil bobbin 3, and the through hole 8 of the primary coil bobbin 2 is formed. Also, the magnetic core 1 is inserted over the through hole 9 of the bobbin 3 for the secondary coil, and the wound secondary coil 1
The heat-resistant film 14 is lapped on the surface of the transformer 3 to form the transformer according to this example. The film 14 functions as a retainer for protecting the secondary coil 13 and for preventing the secondary coil 13 from being frayed from the winding portion 5c.

As described above, according to this embodiment, the bobbin 3 for the secondary coil is integrally formed with the molding resin M for sealing the primary coil 6 with the resin.
Is sealed in the mold resin M, but the secondary coil 13 is wound around the secondary coil bobbin 3 formed of the same mold resin M.

Therefore, when molding the secondary coil bobbin 3 with the molding resin M, or due to environmental changes or temporal changes after the molding, one coil 6 is wound around the primary coil bobbin 2 and the molding resin M ( Even if a void is formed at the interface with the secondary coil bobbin 3), sufficient insulation between the primary coil 6 and the secondary coil 13 can be ensured, and the transformer has high reliability and long life. Can be planned.

Next, modified examples of the above embodiment will be described with reference to FIGS.
It will be explained based on. The same reference numerals are given to those corresponding to those in FIGS. 1 and 2.

FIGS. 4 and 5 show a first modified example, in which the primary coil bobbin 2 is of a single section type, which is different from the above embodiment. Also in this case, the secondary coil bobbin 3 is formed of the mold resin M that seals the primary coil 6 with resin.

FIGS. 6 and 7 show a second modification, which is a laminated type in which the primary coil 6 and the secondary coil 13 are laminated. In this case, the secondary coil bobbin 3 is formed by the molding resin M that seals the primary coil 6 wound around the cylindrical primary coil bobbin 2 with the secondary coil. By winding 13 and wrapping a heat resistant film 14
The transformer according to the modified example is configured.

FIGS. 8 and 9 show a third modification, which is of a type without the bobbin 2 for the primary coil.
In this case, the secondary coil bobbin 3 is formed of the molding resin M in a state where the primary coil 6 is sealed in the molding resin M by insert molding, and the winding portion 5c (primary coil bobbin 3 of the secondary coil bobbin 3 A secondary coil 13 is wound around the portion where the coil 6 is sealed in the vertical direction), and a heat-resistant film 14 is further wrapped to form a transformer according to a third modification.

FIGS. 10 and 11 show a fourth modification, which is a sandwich type one having a three-layer structure in which the primary coil 6 has one layer and the secondary coil 13 has two layers (13a and 13b). Show. In this case, similar to the second modification, the first secondary coil bobbin 3a is formed of the molding resin Ma that seals the primary coil 6 wound around the cylindrical primary coil bobbin 2 with resin. Then, the first-layer secondary coil 13a is wound around the first secondary coil bobbin 3a.

Then, the second secondary coil bobbin 3b is formed of the molding resin Mb (thermosetting resin: unsaturated polyester resin) for resin-sealing the first layer secondary coil 13a. This second secondary coil bobbin 3
The transformer according to the fourth modification is formed by winding the secondary coil 13b of the second layer around b and lapping the heat-resistant film 14.

In any of the above-described modified examples, similar to the above-described embodiments, sufficient insulation between the primary coil 6 and the secondary coil 13 can be ensured, and high reliability and long life of the transformer are achieved. be able to.

In the above-mentioned embodiments and modified examples, as the primary coil 6 and the secondary coil 13, the insulating coated copper wire is used. However, in addition, a metal foil laminated on the insulating film is used, and The foil may be wound in multiple layers to form the primary coil 6 and the secondary coil 13, respectively. In this case, the size of the transformer can be further promoted, and the coupling coefficient can be improved.
It is possible to support a wide range of circuit systems.

[0028]

According to the transformer of the present invention, the insulation performance between the primary coil and the secondary coil can be improved, and the reliability and long life of the transformer can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a transformer for a switching power supply according to this embodiment.

FIG. 2 is a vertical cross-sectional view showing a transformer for a switching power supply according to this embodiment.

FIG. 3 is an explanatory view showing a method of making a secondary coil bobbin according to the present embodiment.

FIG. 4 is a perspective view showing a transformer according to a first modification.

FIG. 5 is a vertical sectional view showing a transformer according to a first modification.

FIG. 6 is a perspective view showing a transformer according to a second modification.

FIG. 7 is a vertical cross-sectional view showing a transformer according to a second modification.

FIG. 8 is a perspective view showing a transformer according to a third modification.

FIG. 9 is a vertical cross-sectional view showing a transformer according to a third modification.

FIG. 10 is a perspective view showing a transformer according to a fourth modification.

FIG. 11 is a vertical sectional view showing a transformer according to a fourth modification.

FIG. 12 is a sectional view showing a transformer for a switching power supply according to a conventional example.

FIG. 13 is an equivalent circuit diagram of a transformer.

FIG. 14 is a perspective view showing a transformer according to another conventional example.

FIG. 15 is a vertical cross-sectional view showing a transformer according to another conventional example.

FIG. 16 is an explanatory diagram showing disadvantages of a transformer according to another conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 magnetic core 2 bobbin for primary coil 3 bobbin for secondary coil 4 partition walls 5a, 5b, 5c winding part 6 primary coil 7 external terminal pin 8, 9 through hole 13 secondary coil 14 film M mold resin

Claims (1)

[Claims] 1. A bobbin having a partition wall is arranged on a coaxial magnetic core, and a primary coil and a secondary coil are separately wound on a plurality of winding portions defined by the partition wall of the bobbin, Further, in the transformer in which the primary coil and the secondary coil are resin-sealed with a molding material, a molding material for resin-sealing one coil of the first coil and the secondary coil and a bobbin of the other coil are provided. A transformer characterized by being integrally formed of the same material.