JP2628524B2 - 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 boosting transformer suitable for use in an inverter for lighting a cold-cathode tube for back lighting of a liquid crystal display device.

[0002]

2. Description of the Related Art A conventional step-up transformer for an inverter is shown in FIG.
It is configured as follows. 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 separately at the collar 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. The center legs 6, 7 of two E-shaped cores 4, 5 are inserted into the hollow portion 3 of the bobbin 2, and the core 4 and the core 5 are fixed to each other. The bobbin 2 and the cores 4, 5 are fixed on an insulating base (not shown) on which terminals are implanted.

[0003]

This type of transformer is
It is necessary to make the display device thin so that it can be mounted in a narrow gap of the display device. 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 It is an object of the present invention to provide a step-up transformer having a small copper loss, a high efficiency, a low profile and a high withstand voltage.

[0005]

SUMMARY OF THE INVENTION A step-up transformer according to the present invention is an insulating transformer having a base portion on which terminals are implanted, a cylindrical winding shaft projecting upward from the base portion, and a flange provided on the upper end of the winding shaft. A bobbin, a primary winding wound around a winding shaft, a secondary winding that is arranged and wound in multiple layers from the inside to the outside and is arranged below the base portion and electromagnetically coupled to the primary winding, A first core having an E-shaped cross section in which a cylindrical central leg is inserted into a bobbin winding shaft, a second flat plate-shaped core butted against the first core with the bobbin interposed therebetween, and a secondary winding And an insulating sheet having a notch near the inner peripheral surface of the secondary winding, and leading a lead wire on the winding start side of the secondary winding from the notch to below the insulating sheet. At the same time, connect the lead wire of the primary winding and the lead wire of the secondary winding to the terminals on different sides of the bobbin, respectively. And wherein the connection configuration.

[0006]

1 to 4 show an embodiment of a step-up transformer according to the present invention. FIG. 1 is an exploded perspective view, FIG. 2 is a plan view, FIG. 3 is a front sectional view, and FIG. It is. The plastic bobbin 10 has multiple terminals on two opposite sides.
It has a base portion 11 in which 21, 22, 23 are implanted, and a cylindrical winding shaft 12 protruding upward from the center of the base portion 11,
A collar 13 is provided at the upper end of the winding shaft 12. Terminals 22 and 23 provided on one side surface of the bobbin 10 are divided into those for connecting a lead wire of the secondary winding 50 and those for external connection. That is, the terminal 22 and the short terminal 23 are configured to be paired one by one and integrally connected inside the base portion 11.

As shown in FIGS. 3 and 4, a low-voltage-side primary winding 30 is wound around the winding shaft 12 of the bobbin 10, and a recess 14 provided on the lower surface of the base 11 has A secondary winding 50 on the high voltage side is attached. The secondary winding 50 located below the base portion 11 is electromagnetically coupled to the primary winding 30 opposed via the base portion 11. As shown in FIG. 8, the secondary winding 50 is a state in which the wire 8 is wound in multiple layers from the inside to the outside in a multilayer manner.
It is hardened like. Such a secondary winding 50
For example, using a so-called self-fusing wire in which a thermoplastic fusible varnish is covered on the outside of a copper wire coated with polyurethane, for example, heating this wire, or applying a solvent, aligning and winding in multiple layers After that, it is obtained by cooling or drying.

Numerals 60 and 70 are cores made of a non-conductive magnetic material. The pair of magnetic cores 60 and 70 are opposed to each other while sandwiching the bobbin 10 from above and below to form a closed magnetic path. As is apparent from FIG. 4, the upper core 60 is a flat plate portion.
61, outer legs 62 integrally formed at both ends thereof, and a flat plate portion 61
The central leg 63 is inserted into the hollow portion of the winding shaft 12 and has an E-shaped cross section having a cylindrical central leg 63 integrally formed at the center of the shaft. On the other hand, the core 70 attached to the lower side of the bobbin 10 has a flat shape.

As shown in FIG. 3 and FIG.
A thin insulating sheet 40 is inserted between 70 to provide a structure in which magnetic saturation hardly occurs. As shown in FIG. 1, the insulating sheet 40 has a through hole 41 slightly larger than the cross section of the central leg 63 of the core 60, and a slit 42 extending from one side surface to the through hole 41.
Is provided. An end of the slit 42 near the through hole 41 is provided with a notch 45 so as to be wide. Further, cutouts 43 are formed at the four corners of the insulating sheet 40 so that the two cores 60 and 70 can be bonded to each other at the four corners of the insulating sheet 40. Notches 44 so that an insulating coagulant such as varnish can be injected into
Is provided.

A lead wire 31 of the primary winding 30 is connected to a terminal 21 planted on one side of the bobbin 10 through the base 11 as shown in FIG. A winding for feedback oscillation or the like may be wound around the winding shaft 12 in addition to the primary winding 30, and a tap may be taken out on the way. In that case, four to six lead wires are connected to each terminal 21.

In the secondary winding 50, the potential difference between the lead wire 51a on the winding start side and the other portion becomes larger as it approaches the outer winding end portion. Therefore, as shown in FIG. 5, the lead wire 51a on the winding start side is connected to the slit 42 so that insulation breakdown does not occur between the lead wire 51a on the winding start side and the portion where the potential difference of the secondary winding 50 is large. The bobbin 10 is pulled out from the notch 45 at the back, passes under the insulating sheet 40, and is connected to the terminal 23 through a groove 15 provided on the lower surface of the bobbin 10. Also,
The lead wire 51b on the winding end side is drawn out of the slit 42 and connected to another terminal 23.

FIG. 6 shows a modification of the insulating sheet 40 in which a notch 45 is provided at the edge of the through hole 41 remote from the slit 42. By doing so, the creeping distance between the lead wire 51a and the portion where the potential difference between the secondary winding 50 is large is increased, and the withstand voltage is further improved. As described above, the secondary winding 50 is preliminarily aligned and wound at another place and hardened. If the insulating sheet 40 is provided with a through hole 41 and a slit 42, before removing the secondary winding 50 from the winding shaft of the winding machine,
Since the slit 42 is opened, the insulating sheet 40 is also attached to the winding shaft from the side, and the lead wire 51 can be guided to the notch 45 or the slit 42 and then bonded and fixed to each other.

FIG. 7 shows still another modification of the insulating sheet 40, in which the slit is omitted and only the cutout 45 is formed in the through hole.
It is provided on the edge of 41. In this case, unlike the insulating sheet 40 with the slit 42, it cannot be attached to the winding shaft of the winding machine from the side, but it is advantageous in terms of withstand voltage.

It is not always necessary to provide the through hole 41 in the insulating sheet 40, but if the through hole 41 is slightly larger than the center leg 63, the insulating sheet 40 can be located between the secondary winding 50 and the core 70. This has the advantage that the lead wire 51 can be passed under the insulating sheet 40 without difficulty because it can move upward in the small gap. In any case, the notch 45 of the insulating sheet 40 may be provided near the inner circumferential surface 55 of the secondary winding 50 (FIG. 5).

As shown in FIG. 8, when the wire 8 is wound in multiple layers in the direction of the arrow, the start portion of the winding and the end portion of the next layer are adjacent to each other. However, in the above-described transformer structure, even if the voltage applied to both ends of the secondary winding 50 is 2 kV, if the secondary winding 50 is wound into, for example, 40 layers, the voltage applied between the two is 2000 ÷ 20. since the 100 V, as in the conventional example 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. Among the step-up transformers for inverters, the voltage on the secondary winding side is small, and
Although there is a voltage of less than 00 V, in order to prevent dielectric breakdown, the height H of the secondary winding 50 may be reduced and the winding width W may be increased.

The shape of a round transformer in which a wire is wound on a winding shaft having a circular cross section is shorter than that of a square transformer, so that when the same performance is realized with the same magnetic material,
This is advantageous in that copper loss is reduced and the volume can be reduced. In particular, when used as an inverter transformer, a large-amplitude resonance current of several tens of kHz flows through the primary winding, so reducing the copper loss of the primary winding is a factor that can greatly contribute to improving the conversion efficiency of the transformer.

If a gap is formed between the pair of cores 60 and 70 by a method such as shaving the center leg 63 irrespective of the insulating sheet 40, the vertical position of the E-shaped core 60 and the flat core 70 is switched. Is also good.

[0018]

According to the present invention, not only a low profile and small bottom area but also a shortened winding wire material can provide an efficient step-up transformer with little copper loss. Also,
Using an insulating sheet inserted between a pair of cores to improve magnetic characteristics, the lead wire on the winding start side of the secondary winding can be insulated from the part with a large potential difference, effectively preventing dielectric breakdown. There are features that can be done.

[Brief description of the drawings]

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

FIG. 2 is a plan view of the transformer.

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

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

FIG. 5 is a bottom view of the transformer excluding a lower core.

FIG. 6 is a plan view showing a second embodiment of the insulating sheet.

FIG. 7 is a plan view showing a third embodiment of the insulating sheet.

FIG. 8 is an explanatory view of a cross section on one side of a winding wound in multiple layers.

FIG. 9 is an exploded perspective view of a conventional transformer.

[Explanation of symbols]

 10 bobbin 11 base 12 reel 30 primary winding 40 insulation sheet 45 notch 50 secondary winding 60 core 63 center leg 70 core

Continuation of the front page (72) Inventor: Akira Shinaki 18th, Gomigaya, Tsurugashima-shi, Saitama Toko Co., Ltd. Saitama Plant 28134 (JP, Y1)

Claims (3)

(57) [Claims] An insulating material having a base portion having terminals implanted on two opposing side surfaces, a cylindrical winding shaft protruding upward from substantially the center of the base portion, and a flange provided at an upper end of the winding shaft. A bobbin, a primary winding wound around the winding shaft, a secondary winding that is arranged and wound in multiple layers from the inside to the outside and is disposed below the base portion and electromagnetically coupled to the primary winding, An outer leg is located on two opposite sides of the bobbin on which the terminal is not provided, and a first core having an E-shaped cross section in which a cylindrical central leg is inserted into a bobbin winding shaft, and the bobbin is sandwiched therebetween. A second core having a flat plate shape butted against the first core, and an insulating sheet having a notch near the inner surface of the secondary winding, which is located below the secondary winding, The lead wire on the winding start side of the secondary winding is pulled out from the notch under the insulating sheet, and the primary winding is removed. A step-up transformer characterized in that a lead wire and a lead wire of a secondary winding are respectively connected to terminals on different side surfaces of a bobbin. 2. The step-up transformer according to claim 1, wherein the insulating sheet is interposed between a first core mounted from above the bobbin and a second core mounted below the bobbin. Wherein said insulating sheet includes a slightly larger circular through-hole than the cross-section of the central leg of the first core, having a slit extending from one side to the through hole, notch portion of the through hole 3. The step-up transformer according to claim 2, which is provided at an edge.