JP2001313221A - Inverter transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that an inverter transformer cannot be easily and greatly thinned. SOLUTION: This inverter transformer is equipped with a lower core 30 that has projections 31 and 32, an upper core 40, a plurality of electrodes 50 that are directly mounted onto the lower surface of the lower core 30, a primary coil 10 that is fitted to the projection 31 that is annularly wound and fixed and a secondary coil 20 that is fitted to the projection 32 that is annularly wound and fixed. At a position close to the projections 31 and 32, cutouts 34 and 35 passing through the lower core 30 are formed. Lead wires 11a and 21a at a side where the winding of the primary and secondary coils 10 and 20 is started are connected to the electrode 50 through the cutouts 34 and 35.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter transformer used in an inverter for lighting a cold cathode discharge tube or the like (hereinafter, referred to as a discharge lamp) for illuminating the back of a liquid crystal display device, and more particularly to a primary winding and a secondary winding. The present invention relates to a structure of a leakage inductance type inverter transformer in which windings are loosely coupled.

[0002]

2. Description of the Related Art FIG. 11 shows a conventional inverter transformer in which a primary winding and a secondary winding are loosely coupled. A primary winding 3 is wound around a bobbin 2 to which a terminal 1 is attached, and a secondary winding 6 is wound around a bobbin 5 to which a terminal 4 is attached. Lead wires of the primary winding 3 and the secondary winding 6 are connected to terminals 1 and 4, respectively. The legs 7a and 7b of the core 7 are inserted into the holes of the bobbins 2 and 5, respectively, and the flat core 8 is abutted against the core 7 to form a closed magnetic path. The projection 7c of the core 7 located between the primary winding 3 and the secondary winding 6 acts to weaken the degree of electromagnetic coupling between the two windings and loosely couple them. The output current of the inverter transformer can be limited by selecting the height of the protrusion 7c so that the coupling coefficient between the two windings becomes a predetermined value suitable for the inverter circuit. As a result, an inverter circuit without a ballast capacitor can be configured, and the luminance efficiency of the discharge lamp can be improved.

[0003]

Since the inverter transformer can be mounted in a narrow gap, there is a strong demand for a thinner transformer. Recently, an extremely thin transformer having a thickness of 2 mm or less has been desired. However, the conventional inverter transformer has a structure including the bobbins 2 and 4, and thus has a limit of about 4 mm in thickness.
An object of the present invention is to further reduce the thickness of a wound-type inverter transformer.

[0004]

An inverter transformer according to the present invention has a lower core 30 having upwardly protruding projections 31 and 32 and having at least a surface made of an insulator, and a lower core 30 having at least a surface made of an insulator. The upper core 40 which forms a closed magnetic path by being brought into contact with the plurality of electrodes 50 directly attached to the lower surface of the lower core 30, and portions other than the lead wires are wound into an annular shape and directly fitted into the protruding portions 31. A primary winding 10 and a secondary winding 20 in which portions other than the lead wires are hardened in an annular shape and directly fitted into the protruding portions 32, and the lower core 30 is located immediately near the protruding portions 31.
Through the notch 34 and the lower core at a position
A notch 35 penetrating through 30 is provided, and the lead wire 11a on the winding start side of the primary winding 10 passes through the notch 34 to
The lead wire 21a on the winding start side of 20 is connected to different electrodes 50 through the cutouts 35, respectively.

[0005]

1 to 5 show an embodiment of an inverter transformer according to the present invention. Numerals 30 and 40 denote a pair of cores made of an insulating magnetic material. On the upper surface of the lower core 30 are integrally formed columnar projections 31 and 32 and two projections 33 projecting upward. The height of the projection 33 is lower than that of the projections 31 and 32.
On opposite two side surfaces of the lower core 30, projecting portions 31, 32 are respectively provided.
Notches 34 and 35, which are formed by slits reaching up to the center, are provided. At the four corners on the lower surface of the lower core 30, electrodes 50 made of a metal plate are provided.
Are attached by bonding, and the end of the electrode 50 is projected outward from the side surface of the lower core 30.

[0006] A self-fused wire is used for the primary winding 10, and portions other than the lead wire 11 are wound into a ring shape. Secondary winding 20
Also, after self-welding wires are aligned and wound in multiple layers, portions other than the lead wires 21 are wound in a ring shape. As shown in FIG. 6, the primary winding 10 and the secondary winding 20 are fitted directly to the protruding portions 31 and 32 without the interposition of a bobbin, and mounted on the lower core 30. Note that a relatively thick wire having a small number of turns is used for the primary winding 10. For this reason, when a thick wire is used, it is possible to obtain a substantially solidified state without using a self-bonding wire.

As shown in FIG. 3, the lead wires 11a and 21a on the winding start side of the primary winding 10 and the secondary winding 20
After being led out to the lower side of the lower core 30 through 4 and 35, it is connected to the upper surface of a different electrode 50 by means such as soldering or welding.
Since the lead wires 11a and 21a on the winding start side pass through the notches 34 and 35 and do not pass through the gap between the winding body and the lower core 30, the primary winding 10 and the secondary winding 20 Is only the thickness of the primary winding 10 and the secondary winding 20 themselves.

The secondary winding 20 having a large potential difference between the winding start and the winding end is connected to the lead wire 21 on the winding start side as described above.
It is desirable that the lead wire 11a be led out to the lower side of the lower core 30, but the lead wire 11a on the primary winding 10 side, which is a low voltage, on the winding start side only needs to pass through the cutout 34, and it is not always necessary to pass the lower side of the lower core 30. Need not be derived. Incidentally, reference numeral 60 in FIGS. 2 and 4 denotes solder.

Protruding from the lower surface of the lower core 30 is a lead wire.
Only the diameters of 11a and 21a and the thickness of the electrode 50 are required. As a wire, the primary winding 10 is generally 0.1 to 0.2 mm,
An extremely thin secondary winding 20 of about 0.03 mm is used. Therefore, by using a thin electrode 50 of about 0.2 mm or less, these protrusion dimensions can be made extremely small.

The lead wires 11b and 21b on the winding end side pass over the lower core 30 and are connected to the upper surface of the electrode 50. A flat upper core 40 is abutted against the lower core 30 from above to form a closed magnetic path. Holes 45 and 46 penetrating through the upper core 40 are formed in the upper core 40 at positions facing the protrusions 31 and 32, respectively. The protruding portions 31, 32 and the upper core 40 are adhered by an adhesive (not shown) injected from the holes 45, 46. Also,
The lower core 30 and the upper core 40 are also fixed to each other at the four corners with an adhesive 70 (FIGS. 4 and 5). Projection 3 provided on lower core 30
The protrusion 33 lower than 1 and 32 acts to reduce the electromagnetic coupling between the primary winding 10 and the secondary winding 20 as in the case of the protrusion 7c in FIG.

FIG. 7 shows another embodiment of the cutouts 34 and 35, which is not a slit but a small through hole. The notches 34 and 35 are respectively provided with the protrusion 31 and the protrusion
It penetrates the lower core 30 at a position closest to 32. in this case,
The primary winding 10 and the secondary winding 20 are connected to the lead wire 11 on the winding start side.
It is sufficient to fit the main body portion wound in an annular shape into the protruding portions 31 and 32 and to incorporate it into the lower core 30 while passing the a and 21a through the cutout portions 34 and 35. When the cutouts 34 and 35 are formed as through holes, the lead wires 11a and 21a on the winding start side are surely separated from the main body of the primary winding 10 and the secondary winding 20 by the lower core. This is advantageous in increasing the dielectric strength.

As shown in FIG. 8, an electrode 50 made of a metal plate is provided.
And a connection part 51 with the lead wires 11 and 21 is formed at a position higher than the lower surface of the lower core 30, and the lead wires 11 and 21 are wound around the connection part 51 and soldered. You can also. The electrode 50 is not limited to a metal plate, and may be directly attached to the lower core 30 by printing or other means.

FIG. 9 shows another embodiment of the upper core 40, in which through holes 44 are provided at four corners where an adhesive is applied. When the adhesive penetrates into the through-holes 44, the bonding strength between the lower core 30 and the upper core 40 increases. The upper core 40 may be provided with a hole for injecting an adhesive similar to the holes 45 and 46 in FIG. In the embodiment, an insulating magnetic material is used for the material of the upper core 40 and the lower core 30, but a conductive magnetic material whose surface is covered with an insulating film can be used.

FIG. 10 shows another embodiment of the inverter transformer. In this structure, two secondary windings 20 are arranged symmetrically with respect to the primary winding 10 so that one inverter transformer can obtain two outputs. In this example, the secondary winding 20 is wound in an elliptical shape in order to reduce the width of the entire transformer.

[0015]

According to the structure of the present invention, the winding type inverter transformer can be made as thin as possible. Upper and lower cores with thickness of 0.7mm and thickness of 0.6
A prototype of an inverter transformer having a total height of about 2 mm using a primary winding and a secondary winding of 1 mm was confirmed to obtain practical characteristics.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of an inverter transformer according to the present invention.

FIG. 2 is a plan view of the transformer.

FIG. 3 is a bottom view of the transformer.

FIG. 4 is a front view of the transformer.

FIG. 5 is a front sectional view of the transformer.

FIG. 6 is a plan view of the transformer with an upper core removed.

FIG. 7 is a bottom view of a transformer showing another embodiment of the cutout portion.

FIG. 8 is an enlarged perspective view of a part of a transformer showing another embodiment of the electrode.

FIG. 9 is a perspective view showing another embodiment of the upper core.

FIG. 10 is a plan view of a main part showing another embodiment of the inverter transformer.

FIG. 11 is a front sectional view of a conventional inverter transformer.

[Explanation of symbols]

 10 Primary winding 20 Secondary winding 30 Lower core 31, 32 Projection 34, 35 Notch 40 Upper core

Claims (5)

[Claims] 1. A lower core having first and second protruding portions projecting upward and having at least a surface made of an insulator, and at least a surface made of an insulator butted against the lower core to form a closed magnetic path. An upper core, a plurality of electrodes directly attached to the lower surface of the lower core, a primary winding in which a portion other than the lead wire is wound into a ring and directly fitted into the first protrusion, and a portion other than the lead wire A second notch which is wound in a ring shape and is directly fitted into the second protrusion, a first cutout penetrating the lower core at a position immediately adjacent to the first protrusion, and a second notch. A second notch penetrating the lower core is provided at a position immediately adjacent to the protrusion, and a lead wire on the winding start side of the primary winding passes through the first notch and a lead on the winding start side of the secondary winding. Wherein the wires are connected to different electrodes through the second notch. Trance. 2. The inverter transformer according to claim 1, wherein the cutouts are slits extending from different side surfaces of the lower core to the first protrusion and the second protrusion, respectively. 3. The inverter transformer according to claim 1, wherein said cutout portion is a through hole. 4. The inverter transformer according to claim 1, wherein the electrodes are made of a metal plate adhered to the lower core. 5. The inverter transformer according to claim 4, wherein a part of the electrode is bent to form a connection portion with a lead wire at a position higher than the lower surface of the lower core.