JPS6331378Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a transformer, which is particularly suitable for small transformers such as switching power supply transformers, but is also applicable to general transformers.

In transformers for switching regulators, each country has safety standards regarding insulation between the primary and secondary windings. For example, in UL (USA) the creepage distance is 3 mm and the insulation layer thickness is 0.7 mm, while in the IEC class (Europe) the creepage distance is 6 mm and the insulation layer thickness is 0.4 mm. Therefore, a transformer for a switching regulator must satisfy these safety standards, but it also needs to have good coupling between the primary and secondary components since switching is performed using high-frequency pulses. Therefore, in such a transformer, a potting structure and a foil wrapping method are used to solve these problems.

FIG. 1 is a front view showing one example, and FIG. 2 is an enlarged sectional view thereof. Conventional transformers generally use an EE or EI type core, and the transformer shown in the figure uses an EE type core. In the figure,
1 is an E-shaped iron core, and 2 is a coil structure. The coil structure 2 is made by winding a porous paper 4, a copper foil 5, and an insulating sheet 6 around a winding frame (bobbin) 3, and hardening these with a resin that impregnates the porous paper 4. The thickness of the bobbin 3 is approximately 1 mm, and the thickness of the copper foil 5 is approximately 30 to 75 μm.
The thickness of the insulating sheet (Mylar) 6 is approximately 16 μm. The copper foil 5 forms a coil winding, in the example shown.
Copper foil 5 ₁ on both outer sides is the primary winding, copper foil 5 ₂ in the middle is 2
This is the next winding. The coil structure 2 is fitted and bonded to the central protruding portion of the E-shaped core as shown in the figure. With this configuration, the resin that has permeated into the porous paper 4 and the surrounding resin are integrated and have a high insulation resistance, so there is an advantage that there is no need to maintain a large creepage distance as described above. However, bobbin 3 is used to insulate the iron core.
However, if there is no porous paper 4 on the outside of the bobbin 3, the bobbin 3 and the resin cannot be considered as one body, so a porous paper 4 is added around the outer periphery of the bobbin 3.
The insulation layer is wound around 0.4 mm, which is uneconomical (increasing cost). Moreover, the transformer becomes larger and the coupling between the primary and secondary orders deteriorates.

The present invention eliminates the need for a bobbin by winding porous paper directly around the iron core in order to eliminate the above-mentioned drawbacks. Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 3 is a front view showing the first embodiment of the present invention;
FIG. 4 is an enlarged sectional view thereof. This embodiment shows a case where a combination of a T (or convex) type and a U (or concave) type iron core is used (hereinafter referred to as "UT type"). In the figure, 1 ₁ is a U-shaped core, 1 ₂
is the T-shaped core, and 1 ₃ is the part of the T-shaped core that becomes the winding core of the coil. Conventional EE type or
With the EI type iron core, it was not possible to wrap porous paper directly around the core, and bobbin 3 had to be used.
With the UT type core, it is possible to wrap the porous paper 4 directly into the 1 ₃ portions of the T type core 1 ₂ . Winding the insulating sheet 6 and copper foil 5 around the outer periphery to form a coil is the same as in the conventional method. The porous paper 4 is impregnated with resin. As the resin for impregnation, silicone resin or polybutadiene resin is suitable. The layer of resin-impregnated porous paper 4 is sufficient to maintain insulation between the copper foils 5 and between the copper foils 5 and the iron core ₁₃ .

With this configuration, the bobbin 3 is no longer necessary, which not only reduces costs and makes the device smaller by 1 mm in thickness, but also improves the coupling coefficient from 0.985 to 0.990. Also, since the porous paper 4 is wound directly around the iron core ₁₃ , there is no backlash.

FIG. 5 is a front view showing a second embodiment of the present invention. This embodiment shows a case where a combination of I-type and C-type iron cores (hereinafter referred to as "CI" type) is used. In the figure, 1 ₁ ' is the C-type core, 1
₂ ' is the I-type core. When using this CI type core, it is possible to assemble it after directly winding the porous paper 4 into the I type core 1 ₂ ', similar to the above-mentioned UT type core.

In the structural example shown in FIGS. 1 and 2, a base that fits into the core together with the bobbin 3 is provided in a part of the coil structure 2 to process the ends of the winding, and the pins planted on the base are The wires from the winding are tied together. However, in the present invention, such a winding end treatment structure cannot be adopted, so some ingenuity is required. Figures 6 and 7 show one example of the winding end treatment structure in the present invention.
To show an example, Fig. 6 is a plan view showing a situation in which a base for tying wire rods is attached to a T-shaped core ₁₂ ;
FIG. 7 is a partially sectional side view showing the actual mounting situation of the base. In FIG. 6, the coil and U-shaped core ₁₁ are omitted for clarity. FIG. 7 shows only the T-shaped core 1 ₂ and the U-shaped core 1 ₁ cut along the line A-A in FIG. 6. Base 7
A plurality of pins 8 are installed in order to tie the wire rod 11, and a plurality of recesses 9 are provided in order to pass the wire rod 11 through. In addition, a plurality of claws 10 are integrally formed on the base 7 in order to sandwich the base 7 between the portions of the T-shaped iron core 1 ₂ other than the winding core 1 ₃ .

In the above description, the case where the base 7 is attached to a UT type iron core is taken as an example, but it can also be attached to a CI type iron core in the same manner.

As explained above, according to the present invention, compared to conventional transformers, a bobbin is not required, so the cost is reduced and the size can be reduced by the thickness of the bobbin.
In addition, many remarkable effects can be obtained, such as an improvement in the coupling coefficient between the primary and secondary components and elimination of backlash.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified and changed in various ways without departing from the gist of the invention as set forth in the claims for utility model registration. For example, the present invention can be applied to any iron core that has a shape that allows porous paper to be directly wound in it, even if it is not a UT type or CI type iron core.

[Brief explanation of drawings]

1 and 2 are views showing the prior art, FIGS. 3 and 4 are views showing the first embodiment of the present invention, FIG. 5 is a view showing the second embodiment of the present invention, and FIGS. FIG. 7 is a diagram showing an example of a coil terminal processing structure according to the present invention. 5 ₁ ... Primary winding, 5 ₂ ... Secondary winding, 4 ... Porous paper, 1 ₃ , 1 ₂ ' ... Iron core.

Claims (1)

[Scope of utility model registration request] In a transformer in which a first winding is wound around a protrusion of an iron core, and a second winding is wound around the first winding with an insulating layer interposed therebetween, the first winding The transformer is wound around the protruding portion of the iron core with porous paper interposed therebetween, and the porous paper is impregnated with resin.