JPH07302721A - Power supply transformer - Google Patents

Abstract

PURPOSE:To provide a small-sized power supply transformer at a low cost. CONSTITUTION:The title power supply transformer is provided with a hollow bobbin 11, a core 12 arranged in the hollow part of the hollow bobbin 11, a primary winding 13 wound around the hollow bobbin 11, a secondary winding 15 constituted of a wire of three-layered insulating structure which is wound on the primary winding 13 via an insulating tape 14, and a primary side pin 16 and a secondary side pin 17 which are arranged on the hollow bobbin 11 and connected with the primary winding 13 and the secondary winding 15, respectively. An insulating board 18 which is extruded upward at the part on the side of the secondary side pin 17 of the hollow bobbin 11 is arranged, and the winding end part 15b of the secondary winding 15 is annexed to the insulating board 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transformer.

[0002]

2. Description of the Related Art In recent years, a large number of types of switching power supply devices using a power transformer have been produced, and in the field of consumer electric appliances, demands for smaller size and lower cost of the switching power supply device are gradually increasing. For this reason, recently, a wire with three layers of insulation structure that has acquired various safety standards has been used for the transformer wire itself, and the insulation structure of this wire is used to separate the wire between the primary winding and the secondary winding. The use of an insulating structure has made it possible to provide a power transformer that simplifies the structure of the transformer and is aimed at downsizing and cost reduction.

An example of such a power transformer is shown in FIG. 4 (outer perspective view) and FIG. 5 (cross-sectional view taken along line BB in FIG. 4).
Shown in. The power transformer 30 includes a hollow bobbin 31 and
The core 32 arranged in the hollow portion of the hollow bobbin 31, the primary winding 33 wound on the hollow bobbin 31, and the primary winding 3
A secondary winding 35 made of a wire having a three-layer insulation structure wound around the insulating tape 34 on the 3 and a primary winding provided on the hollow bobbin 31 and connected to the primary and secondary windings 33 and 35, respectively. Side and secondary side pins 36, 37. In this example, the winding start portion 35 a of the secondary winding 35 is entangled with the pin 37 a of the secondary side pins 37, and the winding end portion 35 a.
b is bound to the pin 37b. Of course, the primary winding 3
The winding start portion and the winding end portion of 3 are also knotted by the pin 36.

In such a power transformer 30, since the coating of the wire of the three-layer insulation structure, which is the secondary winding 35, has a property of being melted by heat, when the primary side and secondary side pins 36 and 37 are soldered. The power transformer is completed by soldering all pins as they are or by putting them in a solder bath and soldering.

[0005]

By the way, in the power transformer 30 as described above, when soldering the pin 37 in which the wire 35 of the three-layer insulation structure is twisted, the heat of the solder is conducted through the wire (that is, copper wire). However, the coating of the three-layer insulation structure is melted by heat up to the portion other than the wire portion that is entangled in the pin 37, and the melted wire portion of the coating does not meet the safety standard.

For this reason, it is necessary to have a structure having a sufficient space distance or creepage distance so that the wire portion with the melted coating can structurally secure a safety distance. In the power transformer 30, the secondary of the hollow bobbin 31 is required. This is dealt with by making the portion on the side pin 37 side project laterally (horizontally) more than the portion on the primary pin 36 side. However, with such a structure, miniaturization of the power supply transformer is greatly restricted, and it becomes impossible to meet the demand for miniaturization of the switching power supply device.

Therefore, the present invention has been made in view of such problems, and an object thereof is to provide a small-sized and low-priced power transformer.

[0008]

In order to achieve the above object, a power transformer of the present invention comprises a hollow bobbin, a core arranged in the hollow portion of the hollow bobbin, and a primary winding wound around the hollow bobbin. A wire, a secondary winding made of a wire having a three-layer insulation structure wound on the primary winding via an insulating material, and a primary side provided in a hollow bobbin, to which the primary and secondary windings are respectively connected. And a secondary side terminal, wherein the hollow bobbin is provided with an insulating member extending upward in a portion on the secondary terminal side, and the winding end portion of the secondary winding is attached to the insulating member. It is characterized by being.

[0009]

According to the power transformer of the present invention, the hollow bobbin is provided with an insulating member extending upward in a portion on the secondary terminal side.
A wire that melts the wire coating due to the heat when soldering the secondary side terminal with the three-layer insulation wire entangled, because the winding end part of the three-layer insulation structure that serves as the secondary winding is attached The length of the portion is sufficiently secured by attaching the wire to the insulating member. Furthermore, the creepage distance between the wire portion where the coating is melted and the primary winding is sufficiently secured by the insulating member, so that the space distance between the two is not required inside the transformer. As a result, the power transformer can be downsized while satisfying the safety standard, the structure of the transformer provided with the insulating member is simple, and the cost can be kept low.

The insulating member provided on the portion of the hollow bobbin on the secondary side terminal side is, as described in the following examples,
It may be an insulating plate separate from the hollow bobbin and attached to the hollow bobbin in the manufacturing process of the transformer, or may be integrally molded on the secondary terminal side of the hollow bobbin. Considering automatic winding of the next winding, it is convenient to use a separate component from the hollow bobbin.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The power transformer of the present invention will be described below based on embodiments. FIG. 1 is a perspective view showing the outer appearance of a power transformer according to the embodiment, and FIG. 2 is a sectional view taken along line AA in FIG.
3 shows a side view of the transformer of FIG. 1 with the insulating plate removed. This power transformer 10 is a hollow bobbin 11
And the core 12 arranged in the hollow portion of the hollow bobbin 11.
A primary winding 13 wound around the hollow bobbin 11; and a secondary winding 15 consisting of a wire having a three-layer insulation structure wound around the primary winding 13 via an insulating tape (insulating material) 14.
And the primary and secondary windings 1 provided on the hollow bobbin 11
The hollow bobbin 11 has a plurality of (five in this embodiment) primary and secondary pins (terminals) 16 and 17 to which 3 and 15 are respectively connected, and a part of the hollow bobbin 11 on the secondary pin 17 side. An insulating plate (insulating member) 18 extending upward is provided, and the winding end portion 15b of the secondary winding 15 is attached to the insulating plate 18.

As can be seen from FIG. 2, the part on the primary pin 16 side of the hollow bobbin 11 and the part on the secondary pin 17 side have substantially the same horizontal length, and the part on the secondary pin 17 side has the same length. An insulating plate 18 having an L-shaped cross section is attached. Insulation plate 1
8 is fixed to the back surface of the portion on the secondary pin 17 side with, for example, an insulating adhesive, and extends upward from the side portion of the portion by a length a. The insulating plate 18 is provided with a secondary winding 15, that is, a winding end portion 15b of a wire having a three-layer insulation structure, and further attached to a secondary pin 17. The insulating plate 1
The upward dimension a of 8 is set to a length that can sufficiently secure the length of the wire portion in which the coating is melted by the heat at the time of soldering the pin 17.

Further, five protrusions 19 are provided on the side surface of the hollow bobbin 11 on the secondary pin 17 side so as to correspond to the five pins 17. In FIG. 3, a winding start portion 15a of the secondary winding 15 is twisted by a pin 17 and further wound around two protrusions 19 as shown in FIG. 3, for example. The insulating plate 18 is attached to the hollow bobbin 11 in a state where the inner surface of the insulating plate 18 is in contact with the protrusion 19 so as to cover the protrusion 19. The winding start portion and the winding end portion of the primary winding 13 are entwined with the primary side pin 16 as in the conventional case.

In the power transformer 10 having such a structure, the coating of the wire 15 having the three-layer insulation structure has a property of being melted by heat. Therefore, the pins 16 and 17 may be soldered as they are, or the pins may be soldered in a solder bath. Can be put in and soldered. At the time of this soldering, the coating of the winding end portion 15b entwined with the pin 17 of the wire 15 having the three-layer insulation structure is melted by heat, and the heat transferred to the wire 15 causes the wire portion near the pin 17, that is, the wire portion. The coating of a part of the winding end portion 15b attached to the outer surface of the insulating plate 18 is melted by heat. However, even if the coating of the wire portion located on the outer surface of the insulating plate 18 is melted, the insulating plate 18 is interposed between the wire portion with the melted coating and the primary winding 13, so that the insulating plate 18 This secures a safe distance from the primary winding 13. Moreover, since the length of the wire portion in which the coating melts is shorter than the upward dimension a of the insulating plate 18,
The insulating plate 18 also sufficiently secures the creepage distance between the wire portion in which the coating is melted and the primary winding 13.

On the other hand, since the winding start portion 15a of the wire 15 is also wound around the protrusion 19, the winding start portion 15a is substantially formed.
Has a long length, and a safe distance can be secured even if the coating is melted by heat during soldering. Further, since the insulating plate 18 is provided so as to cover the protrusions 19, the wire 15
The solder does not adhere to the winding starting portion 15a of the insulating plate 1 when it is soldered to the portion where the winding starting portion 15a is entangled with the pin 17.
8 will be protected.

Since the insulating plate 18 as an insulating member is separate from the hollow bobbin 11 in the power transformer 10, the insulating plate 18 may be attached when the wire 15 having the three-layer insulating structure is automatically wound. it can. Of course, when the insulating member is integrally formed with the hollow bobbin 11, the same effect as that of the above-described embodiment can be obtained, but it is difficult to automatically wind the wire 15.

[0017]

As described above, in the power transformer of the present invention, the wire (secondary winding) having the three-layer insulation structure is formed on the insulating member extending upward in the secondary terminal side of the hollow bobbin. )
Since the winding end part of is attached, the length of the wire part where the coating is melted by the heat at the time of soldering the primary side and secondary side terminals, which separates the primary and secondary windings, is secured sufficiently. Therefore, not only the safety distance between the molten wire portion of the coating and the primary winding is ensured by the insulating member, but also the creepage distance between the molten wire portion of the coating and the primary winding is sufficiently secured. Moreover, since the hollow bobbin has a simple structure in which an insulating member extending upward is provided, the cost can be kept low.

Further, a protrusion is provided in the vicinity of the secondary side terminal of the hollow bobbin, and a winding start portion of a wire having a three-layer insulation structure is wound around the protrusion, whereby a safe distance between the winding start portion and the primary winding is provided. Is also secured by the winding length. Moreover,
Since the protrusion around which the winding start portion of the wire is wound is covered with the insulating member, solder does not adhere to the protrusion during soldering, and the protrusion is protected by the insulating member.

[Brief description of drawings]

FIG. 1 is an external perspective view of a power transformer according to an embodiment.

2 is a cross-sectional view taken along the line AA in FIG.

FIG. 3 is a side view of the power transformer of FIG. 1 with an insulating plate removed.

FIG. 4 is an external perspective view of a power transformer according to a conventional example.

5 is a cross-sectional view taken along the line BB in FIG.

[Explanation of symbols]

 10 Power Transformer 11 Hollow Bobbin 12 Core 13 Primary Winding 14 Insulating Tape (Insulating Material) 15 Secondary Winding (Wire with Three-Layer Insulation Structure) 16, 17 Primary and Secondary Side Pins (Terminals) 18 Insulation Plate (Insulation) Member) 19 protrusion

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihisa Sugimoto 17-7 Yanagitacho, Kadoma City, Osaka Prefecture Yumura Electric Co., Ltd.

Claims (3)

[Claims] 1. A hollow bobbin, a core arranged in the hollow portion of the hollow bobbin, a primary winding wound on the hollow bobbin, and three layers wound on the primary winding via an insulating material. A power transformer comprising a secondary winding made of an insulating wire, and a primary side and a secondary side terminal provided in the hollow bobbin, to which the primary and secondary windings are respectively connected, wherein the secondary side of the hollow bobbin A power transformer, comprising a terminal-side portion provided with an insulating member extending upward, and a winding end portion of the secondary winding being attached to the insulating member. 2. The power transformer according to claim 1, wherein the hollow bobbin has a protrusion near the secondary side terminal, and the winding start portion of the secondary winding is wound around the protrusion. 3. The power transformer according to claim 1, wherein the insulating member is an insulating plate having an L-shaped cross section attached to a portion of the hollow bobbin on the secondary side terminal side.