JP2737067B2 - High frequency step-up 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 small and thin high-frequency step-up transformer suitable for use in an inverter for lighting a cold-cathode tube or the like for illuminating the back of a liquid crystal.

[0002]

2. Description of the Related Art A conventional high-frequency step-up transformer for an inverter is configured as shown in FIG. In the hollow of the bobbin 2 having a plurality of flange 1, the low-pressure side primary winding L ₁ and the high pressure side the secondary winding L ₂ are wound and separated by flange 1. Secondary winding L ₂ to which a high voltage is generated, by further wound by dividing into a plurality of stages in the flange 1, are to be prevented by lowering the potential difference between overlapping lines with dielectric breakdown. In the hollow portion 3 of the bobbin 2, the center legs 6, 7 of the two E-shaped cores 4, 5 are respectively provided.
Are 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) on which terminals were implanted.

[0003]

This type of transformer is
In order to be able to be installed in a narrow gap, it is necessary to make the shape thin. For this reason, the cross-sectional shape of the bobbin 2 becomes a flat rectangular shape, and even if the number of turns is the same, the winding length becomes longer, the conductor resistance increases, and the efficiency decreases. The conventional rectangular transformer has a limit of about 5 mm in terms of thinning because the base is attached under the bobbin and the core, and there is a problem that the copper loss increases remarkably when the thickness is further compressed to increase the width. . Further, since it is necessary to divide winding the secondary winding L _2, winding process is complicated, there are drawbacks that the total volume is increased.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-efficiency, low-profile high-frequency step-up transformer having a small copper loss.

[0005]

According to the present invention, there is provided an insulating member having a base having planted terminals on two opposite sides and a cylindrical winding shaft projecting upward from substantially the center of the base. A bobbin, an inner winding wound around a winding shaft, an outer winding wound around the inner winding, and a pair of magnetic cores that are vertically abutted to form a closed magnetic circuit. Prepared,
Insert the cylindrical center leg provided on at least one core into the bobbin winding shaft, connect the inner winding lead wire and the outer winding lead wire to terminals on different side surfaces of the bobbin, respectively, It is characterized in that the winding width W of the winding is greater than the height H of the winding.

[0006]

FIG. 2 is a front sectional view showing an embodiment of a high-frequency step-up transformer according to the present invention, FIG. 3 is a side sectional view, and FIG. 4 is an exploded perspective view of a main part. Plastic bobbin 10
Base portion 11 having a plurality of terminals 20 planted on two opposing side surfaces
And a cylindrical winding shaft 12 protruding upward from the center of the base portion 11, and a flange 13 is provided at an upper end of the winding shaft 12. The terminal 20 is formed in an imposition mold by extending in the lateral direction so that the lower surface of the tip is located at the same horizontal position as the lower end of the bobbin 10. Further, as is apparent from the bottom view of the bobbin 10 in FIG.
A slit 14 and a slit 15 reaching the vicinity of the winding shaft 12 are provided. A low-voltage side inner winding 30 is wound around the winding shaft 12, and a high-voltage side outer winding 50 is wound outside the inner winding 30 via an insulating ring 40 in a direction orthogonal to the center axis of the winding shaft 12. And an insulating ring 45 is attached to the outside thereof.

Although not shown, the lead wire of the inner winding 30 is drawn through one slit 14 and 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 implanted on the other side of the bobbin 10. As the inner winding 30, a feedback winding and the like may be wound together in addition to the primary winding.

The pair of magnetic cores 60 and 70 are opposed to each other with the bobbin 10 sandwiched from above and below to form a closed magnetic path. As is apparent from FIG. 4, the upper core 60 has a flat plate shape, and the lower core 70 has an E-shaped cross section. Lower core 70
Are a flat plate portion 71 and 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.
And the central leg 73 is inserted into the hollow portion of the winding shaft 12. Although not shown, magnetic saturation occurs when a plastic film is inserted or a gap is provided between the core 60 and the center leg 73 or between the core 60 and the center leg 73 and the outer leg 72. The structure is difficult.

On the lower surface of the bobbin 10, a concave portion 17 sandwiched between thick portions 16 on both sides is formed as shown in FIG. This recess 17
2, the lower end of the lower core 70, the lower end of the bobbin 10, and the lower end of the terminal 20 are located on the same plane. doing.

As shown in FIG. 6, when the wire 8 is wound in multiple layers in the direction of the arrow, the start of the winding and the end of the next layer of any layer are adjacent to each other. However, in the above-described transformer structure, even when the voltage applied to both ends of the outer winding 50 is 2 kV, if the outer winding 50 is wound into, for example, 20 layers, the voltage applied between the two is 2000/10, and 200 V since, as with conventional wound in a plurality of stages of the secondary winding L ₂ in the flange, the potential difference becomes lower breakdown between overlapping wires is prevented. Some high-frequency step-up transformers for inverters have a low voltage on the high-voltage side winding of 1000 V or less, but in order to prevent dielectric breakdown, the height H of the outer winding 50 is reduced and the winding width is reduced. W may be increased.

As shown in FIG. 7, an E-shaped core 80 having the same shape may be used as a pair of cores, and the center legs 83 of both cores 80 may be abutted in the winding shaft 12 of the bobbin 10. The shape of a round transformer in which a wire is wound around a winding shaft with a circular cross section is shorter than that of a square transformer, so that when using the same magnetic material to achieve the same performance, copper loss is reduced. This is advantageous in that the volume can be reduced. In particular, when used as an inverter transformer, several tens
Since a large-amplitude resonance current of kHz flows, reduction of the copper loss of the primary winding is a factor that can greatly contribute to improvement of the conversion efficiency of the transformer.

[0012]

According to the present invention, a high-frequency step-up transformer having a low profile and a small copper loss can be constructed. In particular, by configuring the lower end of each of the lower core, the bobbin, and the terminal so as to be located on the same plane, an imposition type transformer with a further reduced height can be obtained. Further, since the upper surface of the transformer can be configured to be flat, there is an advantage that it can be held by vacuum suction when mounted on a printed circuit board. Since the secondary winding does not have to be dividedly wound in a plurality of stages, there is an effect that the winding process is simplified and the productivity is improved.

[Brief description of the drawings]

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

FIG. 2 is a front sectional view showing an embodiment of a transformer according to the present invention.

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

FIG. 4 is an exploded perspective view in which a part of the transformer is partially cut away.

FIG. 5 is a bottom view of a bobbin in the transformer.

FIG. 6 is an explanatory view of a state in which a wire wound in multiple layers is made into a cross section.

FIG. 7 is a side sectional view showing another embodiment of the transformer of the present invention.

[Explanation of symbols]

 Reference Signs List 10 bobbin 11 base part 12 winding shaft 20 terminal 30 inner winding 50 outer winding 60 core 70 core 73 center leg

Claims (4)

(57) [Claims] 1. An insulating bobbin having a base portion having a plurality of imposition type terminals implanted on two opposing side surfaces thereof, and a cylindrical winding shaft protruding upward from substantially the center of the base portion. An inner winding wound around a winding shaft, an outer winding wound around the outer side of the inner winding, and a pair of magnetic cores which are vertically abutted to form a closed magnetic circuit, and at least one of the cores Insert the cylindrical center leg provided on the core into the bobbin winding shaft, connect the lead wire of the inner winding and the lead wire of the outer winding to the terminals on the different sides of the bobbin, respectively. A high-frequency step-up transformer characterized in that a winding width W is larger than a height H of the outer winding. 2. A pair of cores comprising a first plate-shaped core mounted on the upper side of the bobbin and a second core mounted on the lower side of the bobbin in a cross section E having a central leg. 1. High frequency step-up transformer. 3. The high-frequency step-up transformer according to claim 1, wherein the pair of cores have the same shape having a cross section E and both have a central leg, and the central legs of both cores are abutted on the bobbin winding shaft. 4. A lower surface of the base portion of the bobbin is provided with a concave portion for fitting with the lower core, and a lower end of the lower core, a lower end of the bobbin, and a lower end of the terminal are located on the same plane. 2
A high-frequency step-up transformer according to claim 3.