JPH11273958A - Surface mounted transformer core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optimum step up efficiency, by inserting a plurality of small balls in a junction between an upper and lower cores to provide a gap. SOLUTION: The outside walls 14, 16 of a lower and outer cores 3, 4 have each a thin wall thickness. When the upper face of the outside wall 14 and lower face of the outside wall 16 are butted and bonded, many small balls 7 are laid on junction faces of both to provide an adequate gap H2 clipped with the lower and upper cores 3, 4, the small balls 7 are made of glass or plastics, and grain size is arranged to obtain a gap H2 uniform over the round. As a banding means, e.g. the small balls 7 are compounded with and dispersed in an epoxy resin adhesive, coated on the upper face of the lower core 3 or lower face of the upper core 4, pressed and thermally hardened and the gap size is in a range of 10 to 35 μm, pref. 5 to 35 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer core having a gap between a lower core and an upper core for accommodating a coil, and more particularly to a surface mount type transformer core directly mounted on a printed circuit board. .

[0002]

2. Description of the Related Art Conventionally, among so-called surface mount type transformers mounted on a printed circuit board, there is a transformer in which a gap is provided in a core accommodating a coil for the purpose of improving inductance characteristics. FIG. 5 shows an example in which a gap is formed in such a transformer core. This means that the coil is housed inside the lower core 3 mounted on the printed circuit board 2 and the ring-shaped spacer 5 made of a non-magnetic material is placed on the peripheral wall upper surface 3a.
The upper core 4 is placed on the upper surface. The spacer 5 is used to secure a predetermined gap H1.
It is processed to a predetermined thickness by a non-magnetic material such as plastic or glass, and is bonded to a bonding portion between the lower core 3 and the upper core 4 with an adhesive. As described above, by providing the constant gap H1 between the lower core 3 and the upper core 4 by the spacer 5, the inductance characteristics can be improved and a higher boosting effect can be obtained. That is, as the gap 6 is reduced, the magnetic resistance decreases and the inductance value can be increased. On the other hand, as the gap 6 is increased, the magnetic resistance increases and the inductance value decreases. Can be.

[0003]

However, in the above-mentioned conventional spacer 5, a joint surface for mounting the spacer 5 is required on both the lower core 3 and the upper core 4. For example, an EL drive circuit is required. When the mounting space is limited due to demand for miniaturization or thinning such as a step-up transformer, the transformer core itself is small and thin, so that the joining surface cannot be large. The spacer 5 could not be placed in a stable state. Therefore, the lower core 3 and the upper core 4
Has to be joined as it is, and a sufficient boosting efficiency cannot be obtained.

Accordingly, an object of the present invention is to provide a surface-mounted type in which a desired gap can be set at a junction between a lower core and an upper core even if the transformer core is small, and an optimum boosting efficiency can be obtained. To provide a transformer core.

[0005]

According to a first aspect of the present invention, there is provided a surface mount type transformer core having a gap provided at a joint between a lower core for housing a coil and an upper core. In the above-mentioned surface mount type transformer core, a gap is provided by interposing a plurality of small balls at a joint between the lower core and the upper core.

[0006] A surface mounted transformer core according to a second aspect of the present invention is characterized in that the small sphere is a glass sphere or a plastic sphere.

According to a third aspect of the present invention, in the surface mount type transformer core, the gap is set in a range of 10 to 35 μm.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a surface mount type transformer core according to the present invention will be described with reference to the accompanying drawings. FIGS. 1 and 2 show an embodiment of a surface mount type transformer core according to the present invention. In this figure, the lower core 3 has a flat cylindrical shape having a bottom wall 13 similarly to the above-mentioned conventional example, and a recess 8 for accommodating the coil 10 is provided therein. 20
Is fitted up. Also,
Slits 9a and 9b are formed on both upper sides of the outer peripheral wall 14 to draw out both ends of the coil 10. On the other hand, the upper core 4, like the lower core 3, has a flat cylindrical shape having an upper wall 15, and houses the coil 10 inside an outer peripheral wall 16 that abuts against the outer peripheral wall 14 of the lower core 3. The recess 17 is formed, and the central cylinder 22 stands up.

The outer peripheral wall 14 of the lower core 3 and the outer peripheral wall 17 of the upper core 4 each have a small wall thickness, and when the upper surface 18 of the outer peripheral wall 14 and the lower surface 19 of the outer peripheral wall 17 are abutted and joined, The conventional spacer cannot be mounted. Therefore, in this embodiment, in order to provide an appropriate gap H2 at the joint between the two, a large number of small balls 7 are placed as shown in FIG. 1, and this is sandwiched between the lower core 3 and the upper core 4. . The small ball 7 is made of glass or plastic, and has a uniform gap H over the entire circumference by making the particle diameter uniform.
2 can be obtained. As the joining means, for example, a uniform gap can be secured by mixing and dispersing the small balls 7 in an epoxy resin adhesive, applying the small balls 7 to the upper surface 18 of the lower core 3 or the lower surface 19 of the upper core 4, and thermosetting while pressing. . It is to be noted that the coating may be performed at a plurality of portions at equal intervals, and does not need to be performed over the entire surface. The gap amount can be easily adjusted by changing the particle size of the small ball 7.

Since the surface mount type transformer 1 can be reduced in size and thickness as a whole, it can be applied to an EL drive circuit or the like having a small mounting space as shown in FIG.
In this circuit diagram, EL (electroluminescence)
It has a structure in which a light emitting layer is sandwiched between a transparent electrode and a back electrode, and emits light by applying an AC voltage between the transparent electrode and the back electrode to excite EL molecules in the light emitting layer. It is. Since the applied AC voltage is used in a voltage range of about 35 to 150 V, the surface mount type transformer 1 is used for the purpose of increasing the voltage to this voltage range. Note that L1, L2, and L3 in the circuit diagram represent a primary coil, a secondary coil, and a tertiary coil in the surface mount type transformer 1.
Then, the primary voltage input to the VIN is boosted through the secondary coil and the tertiary coil, and the boosted voltage is applied to the EL to turn on the EL. In this circuit, main oscillation is performed based on the relationship between the resistance of the transistor (Tr) and the inductance of the primary coil (L1), and the secondary coil (L
2) The oscillation is maintained by inputting the sub-oscillation signal of the capacitor (C1) to the base of the transistor (Tr).

Next, FIG. 4 shows the relationship between the inductance value and the EL emission luminance when the size of the gap H2 formed at the joint between the lower core 3 and the upper core 4 is changed. According to the result, when the particle size of the small spheres 7, that is, the gap amount was 25 μm, the luminance was highest at 11.3 cd, and the inductance value at that time was 238 mH. And
As the gap amount becomes smaller than 25 μm, the inductance value increases, and the luminance tends to decrease.
On the other hand, when the gap amount is larger than 25 μm, the inductance value decreases, but the emission luminance tends to gradually decrease. The inductance value fluctuates due to the subtle difference in the gap H2, which affects the boosting efficiency of the surface mount type transformer 1. From the above results, the gap amount at which relatively high luminance can be obtained is in the range of 10 to 35 μm, preferably 1 to 35 μm.
A range of 5 to 35 μm is desirable.

[0012]

As described above, according to the surface mount type transformer core of the present invention, the gap is provided by interposing a plurality of small balls at the joint between the lower core and the upper core. Even with a small transformer core used for a drive circuit, a desired gap can be set at the junction between the lower core and the upper core, and an effect that optimum boosting efficiency is obtained can be obtained.

When an EL drive circuit is formed using the surface-mount type transformer core of the present invention, the gap formed at the junction between the lower core and the upper core is set in the range of 10 to 35 μm. EL can be efficiently emitted.

In addition, by using small spheres having the same particle size, a uniform gap amount can be obtained, and a transformer core having uniform quality can be obtained.

Further, according to the surface mount type transformer core according to the present invention, a desired gap can be obtained only by applying the small balls mixed with the adhesive, so that the assembling work is simple, and only a small transformer core is used. It can be widely applied to medium and large transformer cores, and can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a surface mount transformer core according to the present invention.

FIG. 2 is a sectional structural view of the surface-mount type transformer core.

FIG. 3 is a circuit diagram when the surface mount type transformer is applied to an EL drive circuit.

FIG. 4 is a diagram illustrating a relationship between an inductance value and luminance with respect to a gap amount.

FIG. 5 is a sectional structural view of a conventional surface mount type transformer core.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Surface mount type transformer 3 Lower core 4 Upper core 7 Small ball 10 Coil H2 gap

Claims (3)

[Claims] 1. A surface-mounted transformer core having a gap at a joint between a lower core and an upper core accommodating a coil, wherein a plurality of small balls are interposed at the joint between the lower core and the upper core. A surface-mount type transformer core characterized by having a gap formed. 2. The surface mount type transformer core according to claim 1, wherein the small sphere is a glass sphere or a plastic sphere. 3. The transformer core according to claim 1, wherein the gap is set in a range of 10 to 35 μm.