JP2540856Y2 - 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 backlighting a liquid crystal display device.

[0002]

2. Description of the Related Art The applicant has previously disclosed in Japanese Patent Application Laid-Open No. 6-124842 a low-profile type having a configuration in which a high-voltage side secondary winding is arranged and wound in multiple layers and has a low profile. A good step-up transformer was proposed. The present invention relates to an improvement of this type of step-up transformer, and aims at increasing the withstand voltage.

[0003]

SUMMARY OF THE INVENTION A step-up transformer according to the present invention is an insulating transformer having a base portion having terminals planted on two opposite sides and a cylindrical winding shaft projecting upward from substantially the center of the base portion. A bobbin, a low-voltage-side primary winding wound around a winding shaft, and a high-voltage-side secondary that is arranged and wound in layers from the inside to the outside and arranged below the base portion and electromagnetically coupled to the primary winding. A winding, and a pair of cores, which sandwich the bobbin, the primary winding, and the secondary winding from above and below to form a closed magnetic circuit, and form a lead wire for the primary winding and the secondary winding, respectively. In the step-up transformer connected to the terminal on the different side, attach an insulating sheet between the secondary winding and the lower core, provide a cutout on one side of the lower core, and pull out below the insulating sheet The lead wire at the beginning of winding of the secondary winding With deriving the terminal direction through notch, and wherein the structure coated with insulating resin coated with a lead wire to the insulating sheet in the notch.

[0004]

1 shows an embodiment of the step-up transformer according to the present invention. FIG. 1 is a bottom view, FIG. 2 is a bottom view during assembly, FIG. 3 is an exploded perspective view, and FIG. 4 is a front sectional view. . The plastic bobbin 10 has multiple terminals on two opposite sides.
A base part 11 in which 21, 22, and 23 are implanted; and a cylindrical reel 12 projecting upward from the center of the base part 11.
A collar 13 is provided at the upper end of the. The terminals provided on one side surface of the bobbin 10 are divided into a terminal 23 for connection of the lead wire of the secondary winding 50 and a terminal 22 for external connection.
23 are paired one by one and connected integrally inside the bobbin 10.

[0005] As is apparent from FIG.
A low voltage side primary winding 30 is wound around 12, and a high voltage side secondary winding 50 is attached to the lower surface of the bobbin 10. Bobbin
The secondary winding 50 located below 10 is electromagnetically coupled to the opposed primary winding 30 via the bobbin 10. The secondary winding 50 is
Similarly to the winding on the high voltage side of the step-up transformer disclosed in Japanese Patent Application Laid-Open No. 6-124842, the wires are aligned and wound in multiple layers from the inside to the outside, so that the potential difference between the overlapping wires is reduced so that the wires are solidified. is there. Primary winding on low voltage side
30 is wound in a conventional manner without any particular winding and its lead 31 is passed over the bobbin 10 and connected to a terminal 21 mounted on one side of the bobbin 10.

Reference numerals 60 and 70 denote 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. The upper core 60 has an E-shaped cross section having a flat plate portion 61, outer legs 62 integrally formed at both ends thereof, and a cylindrical center leg 63 integrally formed at the center of the flat plate portion 61. Is the reel
Inserted into 12 hollows. The center leg 63 is slightly shorter than the outer leg 62 so that a gap is formed between the center leg 63 and the butted core 70 so that magnetic saturation hardly occurs.

On the other hand, a core mounted on the lower side of the bobbin 10
70 is a flat plate as a whole, and is provided with a triangular cutout 71 on one side. Then, between the secondary winding 50 and the lower core 70, an insulating sheet 40 provided with a cutout 41 cut from one side surface at the center is attached.

As shown in FIG. 2, the lead wire 51a on the winding start side of the secondary winding 50 is drawn out from the tip of the notch 41 of the insulating sheet 40 to the lower surface of the insulating sheet 40 and formed on the lower surface of the bobbin 10. It is connected to the terminal 23 through the groove 15. Insulating sheet
The lead wire 51a passing below the portion 40 is located in the notch 71 of the lower core 70 as shown in FIG. The lead wire 51 a in the notch 71 is covered with an insulating resin 80 such as an epoxy adhesive applied to the insulating sheet 40.
The lead wire 51b on the winding end side is pulled out from the insulating sheet 40 and connected to another terminal 23.

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. When an output voltage of, for example, 1000 Vrms is extracted from the secondary winding 50 side, 20 to 27 around the lead wire 51a on the winding start side.
An extremely strong electric field of about kV / mm is generated. The value of this electric field greatly exceeds the withstand voltage of air.

However, as shown in an enlarged view in FIG. 5, this step-up transformer includes an outer portion 50a of the secondary winding 50 and a lead wire 51a.
In addition to the interposition of the insulating sheet 40, the lead wire 51a is covered with the resin 80 applied to the insulating sheet 40, and the space between the insulating sheet 40 and the lead wire 51a is filled with the resin 80. In addition, there is no possibility that the lead wire 51a on the winding start side approaches the outer portion 50a of the secondary winding 50 having a large potential difference to cause dielectric breakdown due to corona discharge. Meanwhile, insulation sheet
Since the electric field strength between 40 and the secondary winding 50 is about 1/5 of the electric field strength in the vicinity of the lead wire 51a, a sufficient withstand voltage can be ensured without applying the resin 80 in particular. The work of applying the resin 80 to the insulating sheet 40 and the lead wire 51a can be easily performed with good workability because the notch 71 is provided in the core 70.

It is to be noted that the insulating sheet 40 is formed by inserting a part of the insulating sheet 40 into the butted portion of the core 60 and the core 70 so that the core 60 and the
May also be used for adjusting the gap between them. Instead of the non-conductive magnetic cores 60 and 70, a conductive magnetic core whose surface is covered with an insulator can also be used. The notch may be provided on the E-shaped core 60 side by exchanging the positions of the flat core 70 and the E-shaped core 60.

[0012]

According to the present invention, the lead wire at the beginning of winding of the secondary winding can be easily covered with an insulating resin, and corona discharge may occur between the lead wire and the outer winding part. It is possible to obtain a step-up transformer having a high dielectric strength.

[Brief description of the drawings]

FIG. 1 is a bottom view showing an embodiment of the transformer of the present invention.

FIG. 2 is a bottom view of the transformer during assembly.

FIG. 3 is an exploded perspective view showing a part of the transformer with a cutout.

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

FIG. 5 is a sectional view of an essential part taken along line AA of FIG. 1;

[Description of Signs] 10 Bobbin 12 Winding shaft 30 Primary winding 40 Insulation sheet 41 Notch 50 Secondary winding 51 Lead wire 60 Core 70 Core 71 Notch 80 Insulating resin

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication H01F 31/00 A (72) Inventor Shoichi Utsugi 18 Gomigaya, Tsurugashima-shi, Saitama Toko stock Company Saitama Office (56) References Japanese Utility Model Sho 63-105312 (JP, U) Japanese Utility Model Sho 48-28134 (JP, Y1)

Claims (2)

(57) [Scope of request for utility model registration] 1. A base having terminals implanted on two opposing side surfaces.
Part and an insulating bobbin having a cylindrical winding shaft projecting upward from substantially the center of the base portion, a low-voltage-side primary winding wound around the winding shaft, and a multilayer structure from the inside to the outside. A secondary winding on the high voltage side, which is aligned and wound and arranged below the base portion and electromagnetically coupled to the primary winding, a bobbin and a primary winding,
The secondary winding is sandwiched from above and below, butted against each other and closed
A step-up transformer comprising a pair of cores forming a magnetic path and connecting the lead wires of the primary winding and the secondary winding to terminals on different side surfaces of the bobbin, respectively, between the secondary winding and the lower core. Along with attaching an insulating sheet to the lower core, a notch is provided on one side of the lower core, and a lead wire at the beginning of winding of the secondary winding drawn out below the insulating sheet is led out through the notch in a terminal direction, absolute lead in the notch
A step-up transformer characterized by being coated with an insulating resin applied to an edge sheet. 2. A pair of cores, a first core having an E-shaped cross section having a central leg at the center and outer legs at both ends, and a second core having a flat plate shape.
The outer leg is located on the two opposing sides on the side where the terminals of the bobbin are not provided, and the center leg is inserted into the bobbin winding shaft from above. 2. The step-up transformer according to claim 1, wherein a second core disposed below is abutted, and a notch is provided in the second core.