JPH04137510A - Plane transformer - Google Patents

Abstract

PURPOSE:To improve the conversion efficiency of a plane transformer by constituting one of a plurality of planar windings having a less number of turns of a sheet coil and making the width of the winding equal to those of the other windings. CONSTITUTION:The first and third planar windings 21 and 23 are constituted of planar coils 9 and, while the second planar winding 22 has the smallest number of tunes among the windings 21, 23, and 23 like a base winding 5 connected to the base of a transformer 4, the winding 22 is constituted of, for example, a sheet coil 27. The sheet coil 27 is formed by forming an angular spiral planar coil 29 on an electrically insulating sheet 28 by screen printing, etching, etc., and the width Wx of the coil 27 is made equal to the width Wy of the first and third planar windings. Therefore, the conversion efficiency of this transformer 20 can be improved, since the thickness of the transformer 20 can be reduced and the overlapping plane area of the second winding 22 upon the first and third windings 21 and 23 can be increased.

Description

[Detailed Description of the Invention] [Objective 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 windings.

(Prior Art) Generally, many switch power supplies, lamp lighting devices, etc. are equipped with a transformer, and the lamp lighting device shown in FIG. 4 electrically connects a lamp 3 to a power source 1 via a transformer 2. ing.

The transformer 2 has a base winding 5 connected to the base of the transistor 4 arranged on the primary side of a primary winding 6, and a secondary winding 7 connected to the lamp 3.

This transformer 2 may be configured as a planar transformer 8 shown in FIG. Each of them is composed of a winding 9. This planar winding 9 is obtained by winding a conductor 9a having, for example, a circular vertical cross section in a circular spiral shape on substantially one plane.

And these windings 5. 6. 7 are laminated with electrically insulating films 10 interposed therebetween, and the upper and lower surfaces of this laminate are sandwiched by a pair of upper and lower magnetic materials 11 and 12 such as ferrite or amorphous, with electrically insulating films 10 interposed therebetween.

(Problem to be Solved by the Invention) By the way, the number of turns of the base winding 5 is usually smaller than the number of turns of the secondary windings 6 and 7, and moreover, the number of turns of the base winding 5 is smaller than that of the secondary windings 6 and 7,
have the same diameter, so the winding width Wa of the base winding 5 is equal to the winding width wb of the primary and secondary windings 6 and 7, as shown in FIG.
(Wa<Wb).

Therefore, the coupling coefficient between these windings 5, 6, and 7 is low, and the problem may be that the conversion efficiency of the transformer is reduced.

Therefore, in order to make the winding width Wa of the base winding 5 equal to the winding width wb of the other windings 6 and 7, the base winding 5 is connected to the -th and secondary windings as shown in FIG. It is conceivable to use a conductor 9aa that is thicker than the 6°7 conductor 9a.

However, this increases the diameter of the conductor 9aa of the base winding 5, making the thickness 10 of the planar transformer 8 larger than the thickness t of the one in FIG. It will be done.

Therefore, the present invention was made in consideration of these circumstances, and its purpose is to provide a planar transformer that can increase the coupling rate between windings to improve conversion efficiency and reduce the thickness of the transformer. It is in.

[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, in the present invention, a plurality of planar windings each having a different number of windings are laminated via an electrical insulator, and a pair of magnetic wires are further layered via an electrical insulator. In the planar transformer which is held between two bodies, the one with the least number of turns among the plurality of planar windings is constituted by a sheet coil in which the winding is formed by printing or etching on an insulating sheet, and the sheet coil The winding width of the coil is made equal to the winding width of the other planar winding.

(Function) Among the plurality of planar windings, the winding width of the winding with a small number of turns is made equal to the winding width of the other planar windings. The coupling coefficient between lines can be increased to increase conversion efficiency.

Further, since the planar winding having a small number of turns is formed by a sheet coil formed by printing or etching the winding into a planar shape on an electrically insulating sheet, the planar transformer can be made thinner.

(Example) Hereinafter, an example of the present invention will be described based on FIGS. 1 to 3.

FIG. 1 is a longitudinal cross-sectional view of an embodiment of the present invention, and in the figure, a planar transformer 20 includes, for example, three first, second, and third planar windings 21, 22, and 23 connected to two electric wires. They are laminated with insulating films 24, 24 interposed therebetween, and the upper and lower surfaces of this laminate are sandwiched between a pair of magnetic materials 25, 26, such as ferrite or amorphous, further intervening electric insulating films 24, 24, respectively.

The first and third planar windings 21.23 are, for example, the sixth planar windings 21.23.
The second planar winding 22 is composed of a planar coil 9 shown in the figure, and the second planar winding 22 is a base winding 5 connected to the base of the transformer 4 shown in FIG.
Although the number of windings is the smallest compared to the above, it is constituted by a sheet coil 27 shown in FIG. 2, for example.

The sheet coil 27 is formed by forming, for example, a rectangular spiral plane coil 29 on an electrically insulating sheet 28 by screen printing, etching, etc., and the winding width Wx is set to the first and third widths as shown in FIG. It is formed to be equal to the winding width wy of the planar winding.

Therefore, the planar transformer 20 can be made thinner, and the second planar winding 22 with a smaller number of turns, the first,
The plane area where the third planar windings 21 and 23 overlap increases, increasing their coupling coefficients and increasing conversion efficiency.

Note that the planar coil 29 of the sheet coil 27 has a pair of external lead-out terminals 29a, 2 on both the front and back surfaces of the electrically insulating sheet 28.
9b respectively, while its spiral central end 29c
A through hole 30 is bored in the hole.

The through hole 30 penetrates the electrically insulating sheet 28 in the front and back directions and is electrically connected to the external lead terminal 29b on the back surface.

FIG. 3 shows a modification of the sheet coil 27, in which a pair of external lead terminals 29a and 29b are both formed on the surface side of the electrically insulating sheet 28, and one of the external lead terminals
9b and the spiral center end 29c of the planar coil 29, and the lower part 29e thereof is insulated by an electrical insulator 31. According to this, the through hole 30 can be omitted.

In each of the above embodiments, a case has been described in which the planar spiral of the planar coil 29 of the sheet coil 27 is formed into a rectangular planar shape, but the present invention is not limited to this, and a circular spiral may be used.

Moreover, on the contrary, the spiral shape of the first and third planar windings 2123 may be formed into a rectangular shape.

〔Effect of the invention〕

As explained above, in the present invention, among the plurality of planar windings, the one with a small number of turns is constituted by a sheet coil, and furthermore, the winding width is made equal to the winding width of the other planar windings. The conversion efficiency can be increased by increasing the coupling coefficient of these planar windings.

In addition, since the planar winding having a small number of turns is formed by a sheet coil in which the winding is formed into a planar shape on an electrically insulating sheet by printing or etching, the device can be made thinner.

Therefore, a planar transformer incorporating this planar winding can be made thinner.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a planar transformer according to the present invention, FIG. 2 is a plan view of the sheet coil shown in FIG. 1, FIG. 3 is a plan view of another sheet coil, and FIG. 4 is a plan view of another sheet coil. An electric circuit diagram of a general lamp lighting circuit, Fig. 5 is a vertical cross-sectional view of a conventional planar transformer, Fig. 6 is a plan view of the planar winding shown in Fig. 5, and Fig. 7 is a diagram of another conventional example. FIG. 20... Planar transformer, 21... First planar winding,
22... Second planar winding, 23... Third planar winding, 24... Electrical insulating film, 25.26... Pair of magnetic bodies, 27... Sheet coil, 28 m electricity Insulating sheet, 29... Planar coil, 3o... Through pole, 31... Electrical insulator. Applicant's agent Hisashi Hatano 29σ 9b Building 2em No. 5m

Claims (1)

[Claims] A plurality of planar windings each having a different number of turns are laminated with an electrical insulator in between, and this laminate is further sandwiched between a pair of magnetic materials with an electrical insulator in between. In the planar transformer, one of the plurality of planar windings having a small number of turns is a sheet coil having a winding formed by printing or etching on an insulating sheet, and the winding width of this sheet coil is A planar transformer characterized in that the width of the winding is equal to the winding width of the other planar winding.