JP3469464B2 - Inverter transformer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an inverter transformer used in a DC / AC inverter for lighting a cold cathode ray tube for illuminating the back surface of a liquid crystal display device.

[0002]

2. Description of the Related Art Inverter transformers must be made thin because they can be installed in a narrow space of portable equipment such as digital electronic still cameras and 8 mm video cameras.
As a conventional inverter transformer, there is one as shown in FIG. A core 3 made of a drum-shaped insulating magnetic body having two flanges is fixed on a base 2 made of a synthetic resin in which the terminals 1 are implanted. A secondary winding 4 is wound around a cylindrical winding shaft 3a of the core 3, and a primary winding 5 is wound outside the secondary winding 4. A ring-shaped core 6 is attached so as to surround the core 3.

The inverter transformer shown in FIG. 4 is also known. This is obtained by winding a secondary winding 4 and a primary winding 5 around a cylindrical winding shaft 7c of a synthetic resin bobbin 7 having an upper collar 7a and a lower collar 7b. A pair of cores 8 and 9 abutting each other form a closed magnetic circuit. Although not shown in the figure, the bobbin 7 has terminals implanted therein.

[0004]

The former inverter transformer has a closed magnetic circuit structure which is wound directly around the winding shaft 3a of the insulative core 3 so that the height can be easily reduced, but there is a problem that magnetic flux easily leaks from the upper part. On the other hand, the latter inverter transformer has a closed magnetic circuit structure with little magnetic flux leakage, but has the drawback that it is difficult to reduce the height because the bobbin 7 is used. An object of the present invention is to provide an inverter transformer which has a small magnetic flux leakage and can be made low in height.

[0005]

According to the present invention, there is provided an insulative bobbin having a base portion in which terminals are planted on opposite two side surfaces and a cylindrical winding shaft projecting upward from the center of the base portion. A first core made of an insulating magnetic material having a T-shaped cross section, which has a downward protruding portion at the center of the flat plate portion and is inserted into the hole of the bobbin winding shaft, and A second core made of a magnetic material having a U-shaped cross-section that is abutted against each other to form a closed magnetic path, a secondary winding wound around a bobbin winding shaft, and a primary winding wound outside the secondary winding. And a primary winding and a secondary winding are directly opposed to the flat plate portion of the first core.

[0006]

1 and 2 show an embodiment of an inverter transformer of the present invention. Bobbin 10 made of synthetic resin
Is similar to the shape shown in FIG. 4 except that the upper collar 7a of the bobbin 7 is omitted, and a cylindrical winding shaft 12 protruding upward is integrally formed at the center of the base portion 11. As is apparent from FIG. 2, a plurality of terminals 20 are planted on the two opposite side surfaces of the base portion 11. A secondary winding 30 is wound around the winding shaft 12, and a lead wire is connected to a terminal 20 attached to one side surface of the base portion 11, and a primary winding 40 is wound outside the secondary winding 30. Is connected to the terminal 20 attached to the other side surface of the base portion 11.

Reference numeral 50 designates a core having a T-shaped cross section, which has a downwardly projecting cylindrical portion 52 in the center of the flat plate portion 51, and 60 designates the flat plate portion.
A core having a U-shaped cross section having legs 62 extending upward at both ends of 61. The core 50 is formed of a highly insulating Ni-Zn ferrite material. Core 60 is the same as core 50 Ni-Z
The n-type ferrite material may be used, but it is desirable to use the Mn-Zn-based ferrite material in order to further increase the saturation magnetic flux density and reduce the core loss.

In the core 50, the protrusion 52 is inserted into the hole of the cylindrical winding shaft 12, and the flat plate portion 51 is butted against the leg portion 62 of the core 60 to form a closed magnetic path. The upper surfaces of the primary winding 40 and the secondary winding 30 directly face the flat plate portion 51 of the core 50.

As a method of winding the secondary winding 30 and the primary winding 40 around the winding shaft 12, the core 50 and the bobbin 10 are united to form a winding groove and then wound, or wound in advance. It may be performed by inserting the solidified secondary winding 30 and primary winding 40 into the winding shaft 12.

[0010]

As described above, according to the present invention, an inverter transformer having a closed magnetic circuit structure with less magnetic flux leakage, which is efficient and has low noise, and which can be further reduced in height, can be obtained. As a result of trial manufacture, the conventional structure shown in FIG. 4 was limited to a height of 3 mm, but was 2.5 mm, which was about 20% lower. Since the structure of the bobbin is simple, it is easy to manufacture and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an embodiment of an inverter transformer of the present invention.

[Fig. 2] Side view of the transformer

FIG. 3 is a front sectional view showing a conventional example of an inverter transformer.

FIG. 4 is a front sectional view showing another conventional example.

[Explanation of symbols]

10 bobbins 11 Base part 12 reel 30 Secondary winding 40 primary winding 50 cores 52 Projection 60 core

Claims (2)

(57) [Claims] 1. An insulative bobbin having a base portion in which terminals are planted on opposite two side surfaces and a cylindrical winding shaft projecting upward from the center of the base portion, and a flat portion downwardly at the center. A first core made of an insulative magnetic material having a T-shaped cross section, which has a protruding portion and is inserted into a hole of a bobbin winding shaft, and a closed magnetic path is formed by being abutted against the first core. The first winding includes a second core made of a magnetic material having a U-shaped cross section, a secondary winding wound around a bobbin winding shaft, and a primary winding wound outside the secondary winding. An inverter transformer characterized in that the wire and the secondary winding are directly opposed to the flat plate portion of the first core. 2. The inverter transformer according to claim 1, wherein the second core is made of a conductive magnetic material.