JPH03280409A - Flat transformer - Google Patents

Abstract

PURPOSE:To improve conversion efficiency by heightening coil-to-coil coupling coefficient by a method wherein a plurality of plane coils with which a coil is formed in flat shape, are laminated through the intermediary of an electric insulator, this laminated body is pinched by a pair of magnetic materials through the intermediary of an electric insulator, and the external shape of each of these plane coils is made equal. CONSTITUTION:A flat transformer 11 is formed by laminating, three plane coils 12a, 12b and 12c through the intermediary of sheet-like electric insulators 13 and 13, and both upper and lower surfaces of the above-mentioned laminated body are pinched by a pair of upper and lower magnetic members 14a and 14b through the intermediary of sheet-like electric insulators 13 and 13. The plane coils 12a to 12c are formed by spirally winding a conductor, one of the pair of magnetic members 14a and 14b is placed on a primary side and the other part is placed on a secondary side, and the outside diameter of the plane coils 12a and 12c is made equal. Accordingly, the coupling coefficient between the plane coils 12a to 12c can be enhanced and the conversion coefficient of the transformer can also be improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a small, lightweight, and thin planar transformer suitable as a transformer for a power supply device, an inverter, an oscillator, etc. This invention relates to a planar transformer that improves the coupling coefficient between coils.

(Prior art) Conventional transformers include those in which primary and secondary coils are wound around an iron core, but in this case, the primary and secondary coils are made up of copper wire wound in a coil shape. Therefore, there were limits to miniaturization, weight reduction, and thickness reduction.

On the other hand, in recent years, inductance elements and planar coils such as sliced coils have been proposed in which conductors are printed in a coiled or spiral shape on a printed circuit board.

Sliced coils are made by first spirally winding a conductive strip-shaped thin plate of the required width to form a spiral cylinder, and then slicing this spiral cylinder to the required length in the axial direction. configured.

FIG. 2 shows a plan view of an example of such a planar coil 1, in which a conductor 2 is spirally wound on one plane.

Therefore, it is conceivable to use this planar coil 1 to construct a thin, small, and lightweight planar transformer.

FIG. 3 shows a longitudinal section of an example of this planar transformer 3, which includes, for example, three planar coils la, lb, l.
c are laminated with sheet-like electrical insulators 4, 4 interposed therebetween, and upper and lower surfaces of this laminate are further coated with a pair of upper and lower magnetic materials 5a in the figure via sheet-like electrical insulators 4.4, respectively.
, 5b, one of the pair of magnetic bodies 5a, 5b is configured as a primary side, and the other is configured as a secondary side.

(Problem to be Solved by the Invention) However, in such a planar transformer 3, the outer diameter of the planar coil 1b located in the middle is smaller than the outer diameter of the planar coils lc and la located above and below it. A possible problem is that the coupling coefficient between the planar coil 1a and the IC is low, and the conversion efficiency of the transformer is reduced.

FIG. 4 shows the relative relationship between the difference in the outer diameters of the planar coils 1a to ICs and their coupling coefficients, for example:
If the ratio of the outer diameters of any two of these planar coils 1a to IC is 50%, that is, if there is a difference in outer diameter of 1:2, the ratio of the outer diameters of these two is 100%, In other words, this shows that the coupling coefficient between the two is significantly reduced compared to the case where the diameters are approximately the same.

This is considered to be because if there is a dimensional difference in the outer diameter between the planar coils 1a to 10 on the same earthen floor, magnetic flux leaks into the space formed by the dimensional difference, increasing magnetic loss.

The present invention has been made in consideration of the above circumstances, and its object is to provide a planar transformer that can increase the coupling coefficient between planar coils and increase the conversion efficiency with a simple configuration.

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems, the present invention is configured as follows.

In other words, the present invention is a planar coil formed by laminating a plurality of planar coils each with an electrical insulator interposed therebetween, and sandwiching this laminate between a pair of magnetic materials via each electrical insulator. The transformer is characterized in that each of the planar coils has an equal outer diameter.

(Function) Since the outer diameters of the plurality of planar coils are all equal, the coupling coefficient between these planar coils becomes very high as shown in FIG. 4.

Therefore, according to the present invention, it is possible to increase the coupling coefficient between the plurality of planar coils and increase the conversion efficiency as a transformer.

(Example) Embodiments of the present invention will be described below with reference to FIG.

FIG. 1 is a longitudinal cross-sectional view of one embodiment of the present invention, and in the figure, a planar transformer 11 includes, for example, three planar coils 12.
a, 12b, 12c are sheet-like electrical insulators 13.13
The upper and lower surfaces of this laminate are further sandwiched between a pair of upper and lower magnetic bodies 14a and 14b in the figure with sheet-like electrical insulators 13 and 13 interposed therebetween, respectively.

Each of the planar coils 12a to 12c is constructed similarly to the planar coil 1 shown in FIG. 2, and has a conductor wound in a spiral shape. One of the pair of magnetic bodies 14a and 14b is configured as a primary side and the other as a secondary side.

The outer diameters of the planar coils 12a to 12c are all set to be equal.

Therefore, as shown in FIG.
Since the ratio of the outer diameters of ~12c becomes 100%, their coupling coefficient becomes very high, reaching, for example, 0.95%.

That is, according to this embodiment, the planar coils 12a to 12
It is possible to increase the coupling coefficient between c and improve the conversion efficiency as a transformer.

In the above embodiments, each of the planar coils 12a to 12c is constructed by forming a conductor in a spiral shape, but the present invention is not limited to this, and the planar coils 12a to 12c may be formed in a planar shape. The number of laminated layers may be two or more.

〔Effect of the invention〕

As explained above, in the present invention, since the plurality of planar coils have the same outer diameter, it is possible to increase the coupling coefficient between these coils and improve the conversion efficiency as a transformer.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a planar transformer according to the present invention, and FIG. 2 is a plan view showing the general configuration of a planar coil.
FIG. 3 is a longitudinal cross-sectional view of an example of a planar transformer, and FIG. 4 is a graph showing the relative relationship between the ratio of the outer diameters of a plurality of planar coils and the coupling coefficient. DESCRIPTION OF SYMBOLS 11... Planar transformer, 12a-12c... Planar coil, 13... Electrical insulator, 14a, 14b...
magnetic material.

Claims (1)

[Claims] A planar transformer in which a plurality of planar coils forming a planar coil are laminated through electric insulators, and this laminated body is sandwiched between a pair of magnetic bodies through electric insulators, respectively. A planar transformer characterized by having planar coils each having the same outer diameter.