JPH05283248A - High frequency booster transformer - Google Patents

Abstract

PURPOSE:To reduce copper loss, to enhance an efficiency, to reduce a height, to facilitate a winding operation and to improve productivity. CONSTITUTION:The high frequency booster transformer comprises a a lower bobbin 10 having a base in which terminals 20 are implanted to opposed two sides and a cylindrical winding shaft 12 protruding upward from a center of the base 11, an upper bobbin 30 having a cylindrical second winding shaft 32, and a pair of magnetic cores 60, 70 butted vertically to form a closed magnetic path. A columnar central leg 73 provided at least at one core 70 is inserted into the shaft 12, the shaft 12 is inserted into the shaft 32 to engage the bobbin 30 with the bobbin 10 from above to be fixed. An inner winding is wound on the shaft 12, an outer winding is wound on the shaft 32, and leads of the inner and outer windings are connected to the terminals 20 on the opposite side of the bobbin 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact and thin high-frequency boosting transformer suitable for use in an inverter for lighting a cold cathode tube or the like for illuminating the back surface of a liquid crystal display device.

[0002]

2. Description of the Related Art A conventional high frequency boosting transformer for an inverter is constructed as shown in FIG. A low-voltage side primary winding L ₁ and a high-voltage side secondary winding L ₂ are separately wound by the collar 1 on a hollow bobbin 2 having a plurality of collars 1. The secondary winding L ₂ in which a high voltage is generated is further divided into a plurality of stages by the collar 1 and wound so as to reduce the potential difference between the overlapping lines to prevent dielectric breakdown. In the hollow portion 3 of the bobbin 2, the central legs 6, 7 of the two E-shaped cores 4, 5 are respectively provided.
Is inserted, and the core 4 and the core 5 are fixed to each other. And these bobbins 2 and cores 4, 5
However, the structure was fixed on an insulating base (not shown) in which terminals were implanted.

[0003]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
It needs to be thin so that it can be installed in a narrow gap. For this reason, the bobbin 2 has a flat rectangular cross section, and even if the number of turns is the same, the winding length becomes long, the conductor resistance increases, and the efficiency decreases. In the conventional rectangular transformer, the base is mounted under the bobbin and the core, so that the limit is about 5 mm in terms of thinning, and there is a problem that copper loss increases remarkably when the thickness is further compressed to widen .. In addition, since the secondary winding L ₂ has to be divided and wound, the winding work is complicated and the total volume is increased.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high frequency boosting transformer having a small copper loss, a high efficiency, a low profile, and easy winding.

[0005]

According to the present invention, there is provided an insulating material having a base portion in which a plurality of terminals are planted on opposite two side surfaces and a cylindrical first winding shaft projecting upward from the base portion. A lower bobbin and an upper bobbin having a cylindrical second winding shaft;
A pair of magnetic cores that are vertically butted to form a closed magnetic path, at least one of the cores has a section E shape having a cylindrical central leg, and the central leg is inserted into the first winding shaft. At the same time, the first winding shaft is inserted into the second winding shaft, the upper bobbin is fitted and fixed to the lower bobbin from above, and the inner winding is wound around the first winding shaft. An outer winding is wound around a winding shaft, and the lead wire of the inner winding and the lead wire of the outer winding are connected to terminals on different side surfaces of the lower bobbin.

[0006]

2 to 4 show an embodiment of a high frequency boosting transformer according to the present invention, and FIG. 2 is an exploded perspective view of a main part,
3 is a front sectional view, and FIG. 4 is a side sectional view. The lower plastic bobbin 10 has multiple terminals 20 on opposite sides.
A base portion (11) in which is planted and a cylindrical winding shaft (12) projecting upward from the center of the base portion (11) are provided, and a flange (13) is provided on the upper end of the winding shaft (12). As is apparent from FIG. 3, the terminal 20 is laterally extended so that the lower surface of the tip end thereof is in the same horizontal position as the lower end of the lower bobbin 10, and is molded into an imposition die. A slit 14 and a slit 15 reaching the vicinity of the winding shaft 12 are provided at the centers of the two side surfaces of the base portion 11 on which the terminals 20 are planted.

The upper bobbin 30 is provided with a cylindrical winding shaft 32 and a collar 33, and a hook-shaped engaging piece 36 is provided at the lower end of the winding shaft 32. The through hole 31 of the winding shaft 32 is formed larger than the diameter of the collar 13 of the lower bobbin 10. The base portion 11 has grooves 16 on the opposite side surfaces of the slits 14 and 15 corresponding to the locking pieces 36.
Has been formed. The upper bobbin 30 has a locking piece 36 inserted into the groove 16 while inserting the winding shaft 12 into the through hole 31 of the winding shaft 32, and fitted and fixed to the lower bobbin 10. And the lower bobbin
The inner winding 40 on the low voltage side is wound around the winding shaft 12 of 10
On the winding shaft 32 located outside the winding shaft 40, the outer winding 50 on the high voltage side is wound in multiple layers in a direction orthogonal to the central axis of the winding shaft 12. To apply windings to this transformer, for example, the lower bobbin 10 is held by a chuck of a winding machine, the chuck is rotated to wind the inner winding 40 around the winding shaft 12, and then the upper bobbin 30 is lowered. Attach to bobbin 10 and rotate the chuck again to
The outer winding 50 may be wound around.

Although not shown, the lead wire of the inner winding 40 is drawn out through one slit 14 and is connected to a terminal 20 implanted on one side surface of the bobbin 10. The lead wire of the outer winding 50 is pulled out through the other slit 15,
It is connected to a terminal 20 that is planted on the other side surface of the bobbin 10. As the inner winding 40, a feedback winding or the like may be wound together with the primary winding. The engagement piece 36 of the upper bobbin 30 has an inner winding 40 and an outer winding in the middle of the slits 14 and 15.
Increase the creepage distance between 50 to ensure separation between both windings and prevent dielectric breakdown.

The pair of magnetic cores 60 and 70 are abutted against each other with the lower bobbin 10 sandwiched therebetween from above and below to form a closed magnetic circuit. The upper core 60 has a flat plate shape, and the lower core 70 has an E-shaped cross section. The lower core 70 has a flat plate portion 71, outer legs 72 integrally formed at both ends thereof, and a cylindrical central leg 73 integrally formed at the center of the flat plate portion 71.
Is inserted into the through hole 17 of the winding shaft 12.

As shown in FIG. 5, when the wire rod 8 is wound in multiple layers in the direction of the arrow, the winding start portion and the winding end portion of the next layer are adjacent to each other. However, in the above transformer structure, even if the voltage applied to both ends of the outer winding 50 is 2 kV, if the outer winding 50 is wound in 20 layers, for example, the voltage applied between the two is 2000/10, which is 200 V. Therefore, similarly to the conventional example in which the secondary winding L ₂ is divided into a plurality of stages and wound by the collar, the potential difference between the overlapping wire rods is reduced and dielectric breakdown is prevented. Some high-frequency step-up transformers for inverters have a voltage on the high-voltage side that is as low as 1000V or less, but in order to prevent insulation breakdown, the height H of the outer winding 50 should be reduced to reduce the winding width. W should be increased.

As a pair of cores, an E similar to the core 70 is used.
Two shaped cores may be used and the central legs of both cores may be abutted in the winding shaft 12. Further, as shown in FIG. 6, a hook-shaped protrusion 38 is provided on the inner side of the winding shaft 32 of the upper bobbin 30, and the protrusion 38 is engaged with the collar 13 of the lower bobbin 10 to move the upper bobbin 30 and the lower bobbin 10 together. It may be configured to be integrated. In this case, the portion of the lower bobbin 10 to be inserted into the groove 16 can be replaced with the protrusion 37 having no hook. The shape of the round transformer, in which the wire is wound around a winding shaft with a circular cross-section, has a shorter winding wire compared to a rectangular transformer, so copper loss is reduced when the same performance is achieved with the same magnetic material. It is advantageous in that the volume can be reduced. In particular, when used as an inverter transformer, a large amplitude resonance current of several tens of kHz flows in the primary winding, and therefore reduction of copper loss in the primary winding is a factor that can greatly contribute to improvement in conversion efficiency of the transformer.

[0012]

According to the present invention, it is possible to construct a high-frequency step-up transformer having a low profile and a small copper loss. In addition, the secondary winding does not have to be divided into multiple windings, and the inner winding and outer winding can be provided while the lower bobbin is held by the chuck of the winding machine, so the winding process can be automated. It is easy to improve productivity.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a conventional transformer

FIG. 2 is an exploded perspective view of essential parts showing an embodiment of a transformer of the present invention.

FIG. 3 is a front sectional view of the transformer.

FIG. 4 is a side sectional view of the transformer.

FIG. 5 is an explanatory view of a cross-section of a wire wound in multiple layers.

FIG. 6 is a front sectional view showing another embodiment of the bobbin.

[Explanation of symbols]

 10 Lower bobbin 11 Base portion 12 First winding shaft 20 Terminal 30 Upper bobbin 32 Second winding shaft 40 Inner winding 50 Outer winding 60 Core 70 Core 73 Central leg

Claims (1)

[Claims] 1. An insulative lower bobbin having a base portion in which a plurality of terminals are planted on opposite two side surfaces and a cylindrical first winding shaft protruding upward from the base portion, and a cylindrical second bobbin. An upper bobbin having a winding axis and a pair of magnetic cores that are vertically butted against each other to form a closed magnetic path, and at least one of the cores has a cross-section E shape having a cylindrical central leg, and the central leg is Insert the first winding shaft into the first winding shaft, insert the first winding shaft into the second winding shaft, fit the upper bobbin into the lower bobbin from above, and fix the inner bobbin inside. A winding is wound, an outer winding is wound around a second winding shaft, and the lead wire of the inner winding and the lead wire of the outer winding are connected to terminals on different side surfaces of the lower bobbin, respectively. High frequency boost transformer.