JP3488868B2 - Planar coils and transformers - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plane coil and a plane transformer having a winding formed by spirally arranging flat conductors.

[0002]

2. Description of the Related Art Planar coils and transformers are used as choke coils and transformers in switching power supplies and the like. The plane coil and the plane transformer have windings made of a conductor pattern formed by spirally arranging flat conductors. In a flat transformer or a flat coil having a plurality of windings, a plurality of windings are stacked in the thickness direction via an insulating layer.

Among flat coils and flat transformers, those having a relatively small output current are formed by stacking a spiral conductor pattern, an insulating layer and a magnetic layer by a thin film forming technique such as sputtering. Further, among the planar coils and the planar transformers, those having a medium output current include, for example, a double-sided printed circuit board on which a spiral conductor pattern is formed on each surface by etching the conductor layer on each surface with an insulating layer interposed therebetween. There is used a printed coil formed by stacking the conductive plates, or a coil formed by stacking spiral conductor patterns formed by punching a conductive plate with an insulating layer interposed therebetween. In these coils, a hole penetrating in the thickness direction is formed in the central portion of the spiral conductor pattern, and a magnetic body such as an EE type ferrite core is inserted into this hole.

The flat coil and the flat transformer as described above can be made thin, and are therefore used particularly in small and thin switching power supplies.

[0005]

In recent years, due to the decrease in operating voltage of ICs and the increase in current accompanying the increase in the degree of integration of ICs (integrated circuits), switching power supplies are required to be downsized and to be increased in current. There is. The loss due to the resistance of the conductor in the choke coil or transformer, so-called copper loss, increases in proportion to the square of the current value. Therefore, in the plane coil and the plane transformer used as the choke coil and the transformer, reduction of the resistance value of the conductor is an important issue.

Switching elements such as FETs (field effect transistors), which are one of the main components of a switching power supply, have been reduced in loss and miniaturized with the progress of semiconductor technology. On the other hand, magnetic parts such as choke coils and transformers, which are the other main parts of the switching power supply, are difficult to miniaturize. Therefore, the volume ratio of the magnetic component to the entire switching power supply tends to increase. Although magnetic components have been progressing toward miniaturization, they are largely due to the higher switching frequency associated with the progress of the above switching elements. However, when the switching frequency becomes higher, the core of the coil or the transformer can be downsized or the loss can be reduced, but the problem that the copper loss, which is the loss in the conductor, is increased due to the effect of the skin effect.

By the way, conventionally, the width of each turn of the winding in the plane coil or the plane transformer is often constant. However, in this case, there is a problem that the resistance of the outer portion of the winding becomes large, and as a result, the resistance of the entire winding becomes large.

On the other hand, Japanese Unexamined Patent Publication (Kokai) No. 5-226155 discloses a technique of increasing the width of the winding as the distance from the center increases so that the copper loss of each portion of the winding in the coil becomes the same. ing. This technique uses a complex formula to determine the width of each part of the winding. Further, Japanese Patent Application Laid-Open No. 7-37728 also discloses a technique of increasing the width of the winding as the distance from the center increases so that the copper loss of each portion of the winding in the coil becomes the same or almost the same. . In any of these techniques, the ratio Ri / W, which is the ratio of the radius Ri of the inner peripheral portion of each turn of the winding to the width W of each turn of the winding, is made constant, thereby The copper loss of each part of the winding is made the same everywhere, and the copper loss of the entire coil is minimized under the limited space constraint.

However, by making the above Ri / W constant, does the copper loss of each part of the winding in the coil become the same everywhere, and whether the copper loss of the whole coil is minimized? Is not proven.

The present invention has been made in view of the above problems, and an object thereof is to provide a plane coil and a plane transformer in which windings are arranged so that loss is minimized in a limited space. is there.

[0011]

The plane coil of the present invention comprises:
A winding is formed by arranging a flat conductor in a spiral shape, and the winding includes a winding portion of N turns (N is an integer of 2 or more), and n turns (n Is an integer of 1 or more and N or less)
_i (n), the radius of the outer peripheral portion and r _o (n), the innermost winding radius r _{mi n} of the inner peripheral portion of the portion, the innermost winding and the radius of the outer periphery of the outermost winding portions Difference W from the inner radius of the part
r _i (n) and r _o (n) are minimized so that the value of A represented by the equation (1) is minimized when _total and the distance D between the winding portions between adjacent turns are given. Is stipulated. However, r _i (1) = r _min , r _i (n + 1) −r _o
(n) = D and r _o (N) −r _i (1) = W _total .

[0012]

[Equation 3]

In the planar coil of the present invention, the resistance value of the entire winding is set by setting r _i (n) and r _o (n) so that the value of A expressed by the equation (1) is minimized. Is minimized, resulting in a minimum loss in the entire winding. In the present application, the winding portion refers to a portion for one turn of the entire winding.

In the planar coil of the present invention, a plurality of windings are provided, and the plurality of windings may be laminated in the thickness direction via an insulating layer and connected in parallel or in series.

The plane transformer of the present invention comprises a plurality of windings formed in a plane and stacked in the thickness direction, and an insulating layer arranged between the windings, and is one of the plurality of windings. Part of the plurality of windings is a secondary winding, and at least one of the plurality of windings is a primary winding and at least one of the plurality of windings is a secondary winding. A winding of N turns (N is an integer of 2 or more) formed by arranging flat conductors in a spiral shape, and is the nth turn (n is an integer of 1 or more and N or less) winding from the inside. The radius of the inner circumference of the part is r _i (n), the radius of the outer circumference is r _o (n), the radius r _min of the inner circumference of the innermost winding part, and the outer circumference of the outermost winding part. difference W _total of the inner peripheral portion of the radius of the innermost winding portions, and adjacent when the distance D between the winding portions is given in between turns of the above formula ( ) Represented by r so that the value becomes the minimum A _i (n) and r _o (n) in which is defined.

The flat transformer of the present invention is expressed by the equation (1).
R to minimize the value of A _i(n) and r_o(n)
By setting, the resistance value of the entire N-turn winding is maximized.
Small, resulting in losses in the entire N-turn winding
Is minimized.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. [First Embodiment] First, the structure of a planar coil according to a first embodiment of the present invention will be described with reference to FIGS. 1 is a plan view of the planar coil according to the present embodiment, and FIG. 2 is a sectional view taken along the line AA in FIG. The planar coil according to the present embodiment includes a disk-shaped insulating layer 10 and N-turn (N is an integer of 2 or more) winding 11 formed on one surface of the insulating layer 10. . FIG. 1 shows a winding 11 having 5 turns as an example.
A circular hole 10a is formed in the central portion of the insulating layer 10. The winding wire 11 is arranged in a region between the outer peripheral portion of the hole 10 a and the outer peripheral portion of the insulating layer 10. Further, a core (magnetic core) can be inserted into the hole 10a.

The winding 11 is constituted by a conductor pattern formed by spirally arranging flat conductors including foils. Copper, for example, is used as the conductor. Through holes 12 penetrating the winding 11 and the insulating layer 10 are formed at positions of both ends of the winding 11. The through hole 12 is used, for example, as a terminal of a planar coil or as a connecting portion when connecting a plurality of planar coils in parallel or in series.

The planar coil according to the present embodiment may be manufactured, for example, by etching a conductor layer in a printed board having a conductor layer formed on one surface of an insulating substrate, or by punching a conductor plate. May be. Also,
It may be manufactured by forming a conductor pattern on one surface of the insulating substrate by a thin film forming technique such as a sputtering method.

In the flat coil according to the present embodiment,
The wire 11 includes the winding portion of N turns,
Inner circumference of the winding part of the third (n is an integer from 1 to N)
R is the radius (hereinafter called the inner radius) of r_i(n), half of the outer circumference
The diameter (hereinafter referred to as the outer radius) is r_o(n), the innermost
Inner radius r of winding_min, Outer radius of outermost winding part
And the inner radius of the innermost winding part W_total,and
Given the distance D between windings between adjacent turns
The value of A represented by the following equation (1) is
To be r_i(n) and r_o(n) is defined. However
Then r_i(1) = r _min, R_i(n + 1) -r_o(n) = D, r_o(N)-
r_i(1) = W_totalIs. Logx is the natural logarithm of x
is there.

[0021]

[Equation 4]

The winding 1 is set by setting r _i (n) and r _o (n) so that the value of A represented by the equation (1) is minimized.
The overall resistance of unity 1 is minimized, so that the overall loss in winding 11 is minimized. Hereinafter, this will be described in detail.

First, the thickness t, the inner radius r, and the outer radius r + dr
Consider the ring-shaped conductor pattern of. If the width dr is sufficiently small, the resistance value of this conductor pattern is (2πr
It may be expressed by xρ) / (t × dr). Here, ρ is the volume resistivity of the conductor. Therefore, the conductance of the conductor pattern, that is, the reciprocal of the resistance value, is (t × dr) / (2π
r × ρ).

Inner radius r_i, Outer radius r_oThe ring-shaped conductor
The turn has a ring shape with a minute width dr as described above.
If the conductor patterns are equivalent to being connected in parallel
Conceivable. Therefore, thickness t and inner radius r_i, Outer radius r_oof
The conductance of the ring-shaped conductor pattern is
As in (2), (t × dr) / (2πr × ρ) is r _i
~ R_oCan be obtained by integrating in the range
It

[0025]

[Equation 5]

The resistance value R of the ring-shaped conductor pattern having the thickness t, the inner radius r _i , and the outer radius r _o is the reciprocal of the conductance of this conductor pattern, and is therefore expressed by the following equation (3).

[0027]

[Equation 6]

The winding 11 consisting of N turns of winding is
It is considered to be equivalent to a case where N ring-shaped conductor patterns (winding portions) are connected in series. Therefore, the resistance value R _total of the N-turn winding 11 as a whole is _calculated by the following equation (4).
It is represented by.

[0029]

[Equation 7]

Therefore, the inner radius r of the innermost winding portion is
Winding 1 is given given _min , the difference W _total between the outer radius of the outermost winding part and the inner radius of the innermost winding part, and the distance D between the winding parts between adjacent turns.
In order to minimize the resistance value of 1 as a whole, r _i (n) and r _o (n) may be set so that the value of A represented by the above equation (1) is minimized.

The values of r _i (n) and r _o (n) that minimize the value of A are difficult to obtain analytically, but can be obtained by numerical calculation using a computer.

Next, an example of the plane coil according to the present embodiment will be described, and a result of comparison of calculated resistance values between the plane coil of the example and the plane coil of the comparative example will be described.

The planar coil of the first embodiment is provided with a 5-turn winding 11 as shown in FIGS. In this plane coil, copper is used as the conductor forming the winding 11, the thickness t of the conductor is 0.5 mm, the inner radius r _min of the innermost winding portion is 4 mm, and the outer radius of the outermost winding portion is And the inner radius of the innermost winding part W _to
tal was 12 mm, and the distance D between the winding portions between adjacent turns was 0.7 mm. For this plane coil, the inner radius r _i (n) and the outer radius r _o (of the winding portion for each turn when the value of A represented by the equation (1) is minimized by numerical calculation using a computer. n)
The resistance value R _{total of the} entire winding 11 was obtained. The volume resistivity of copper was 1.72 × 10 ⁻⁸ (Ωm). Further, hereinafter, the width r _o (n) −r _i (n) of the winding portion for each turn is W (n)
It is represented by.

FIG. 3 is a plan view of the planar coil of the first comparative example. The planar coil of the first comparative example has a disk-shaped insulating layer 110 and 5 formed on one surface of the insulating layer 110.
And a winding 111 of the turn. In this planar coil, the width W (n) of the winding portion for each turn is constant. The other conditions in the planar coil of the first comparative example are the same as those of the first embodiment.

FIG. 4 is a plan view of the planar coil of the second comparative example. The planar coil of the second comparative example has a disk-shaped insulating layer 120 and 5 formed on one surface of the insulating layer 120.
And a winding 121 of the turn. In this planar coil, the ratio r _i (n) / W (n) of the inner radius r _i (n) of the winding portion and the width W (n) of the winding portion for each turn is constant. Other conditions in the planar coil of the second comparative example are the same as those of the first embodiment.

The width W (n) of the winding portion for each turn and the resistance value R _{total of the} entire winding in each of the planar coils of the first embodiment, the first comparative example and the second comparative example are as follows. It will be as shown in the table below.

[0037]

[Table 1]

As can be seen from the above table, in the planar coil of the first embodiment, the resistance value R _{total of the} entire winding is
It is possible to reduce by 10.63% compared with the planar coil of the comparative example of
It can be reduced by 0.38% as compared with the planar coil of the second comparative example.

Although not shown, the plane coil of the second embodiment is provided with a four-turn winding 11. In this planar coil, copper is used as the conductor forming the winding 11,
The thickness t of the conductor is 0.06 mm, the inner radius r _min of the innermost winding portion is 3 mm, and the difference W _total between the outer radius of the outermost winding portion and the inner radius of the innermost winding portion is 5 mm. , The distance D between windings between adjacent turns is 0.2m
m. For this plane coil, the inner radius r _i (n) and the outer radius r _o (of the winding portion for each turn when the value of A represented by the equation (1) is minimized by numerical calculation using a computer. n) was obtained, and the resistance value R _{total of the} entire winding 11 was obtained.

The plane coil of the third comparative example is provided with a winding of 4 turns, and the width W (n) of the winding portion for each turn is constant. The other conditions in the planar coil of the third comparative example are the same as those of the second embodiment.

The plane coil of the fourth comparative example is provided with a winding of 4 turns, and the ratio r between the inner radius r _i (n) of the winding portion and the width W (n) of the winding portion for each turn. _i (n) / W (n) is constant. The other conditions in the flat coil of the fourth comparative example are the same as those of the second embodiment.

The width W (n) of the winding portion for each turn and the resistance value R _{total of the} entire winding in the respective planar coils of the second embodiment, the third comparative example and the fourth comparative example are as follows. It will be as shown in the table below.

[0043]

[Table 2]

As can be seen from the above table, in the planar coil of the second embodiment, the resistance value R _{total of the} entire winding is
It can be reduced by 6.31% as compared with the plane coil of the comparative example and 0.05% as compared with the plane coil of the fourth comparative example, which is a slight reduction.

As described above, according to the planar coil of this embodiment, r _i (n) and r _o (n) are set so that the value of A represented by the equation (1) is minimized. Since it is set, the resistance value of the entire winding 11 can be minimized. Therefore,
According to the present embodiment, the winding 11 can be arranged so that the loss is minimized in the limited space, and as a result, the loss due to the resistance of the conductor can be reduced. Further, according to the flat coil according to the present embodiment, the flat coil in which the width W (n) of the winding portion for each turn is constant and the inner radius r _i (n) of the winding portion for each turn are provided. And winding width W
The resistance value of the entire winding 11 can be reduced as compared with a planar coil in which the ratio r _i (n) / W (n) with respect to (n) is constant.

[Second Embodiment] Next, the second embodiment of the present invention will be described.
The configuration of the planar coil according to the embodiment will be described. 5 is a plan view of the planar coil according to the present embodiment, FIG. 6 is a right side view of the planar coil shown in FIG. 5, and FIG. 7 is a sectional view taken along line BB in FIG. As shown in these drawings, the planar coil according to the present embodiment includes a conductor pattern formed of a flat conductor including a foil shape, and four windings 21 to 21 stacked in the thickness direction. 24,
It is provided with three insulating layers 20 arranged between the respective windings, and E-shaped cores 25A and 25B mounted on a laminated body of the windings 21 to 24 and the insulating layer 20. Copper, for example, is used as the conductor.

FIG. 8 is a plan view showing the uppermost winding 21 and the insulating layer 20 therebelow, and FIG. 9 is a plan view showing the second winding 22 from the top and the insulating layer 20 below it. 10 is 3 from the top
A plan view showing the th winding 23 and the insulating layer 20 thereunder,
11 is a plan view showing the lowermost winding 24, and FIG. 12 is a plan view showing the insulating layer 20.

As shown in FIG. 12, the insulating layer 20 has a substantially disk shape. A circular hole 20a is formed in the central portion of the insulating layer 20. Further, the insulating layer 20 has a bulging portion 20b in which a part of the outer peripheral portion bulges outward in the radial direction. The windings 21 to 24 are arranged in a region between the outer peripheral portion of the hole 20a and the outer peripheral portion of the insulating layer 20.

Each of the windings 21 to 24 is composed of a conductor pattern formed by spirally arranging a flat conductor including a foil. Also, the windings 21 to 24
Has N turns (N is an integer of 2 or more).
In FIGS. 8 to 11, as an example, the winding 2 having 5 turns is used.
1 to 24 are shown.

As shown in FIGS. 8 and 10, the winding 2
1, 23 are wound clockwise from the inner side to the outer side. The outer ends of the windings 21 and 23 are arranged at the right side of the bulging portion 20b of the insulating layer 20. Through holes 26a are formed at positions where the outer ends of the windings 21 and 23 are arranged so as to penetrate the three insulating layers 20 and the windings 21 and 23. Winding 21,
The outer ends of 23 are electrically connected to each other through the through holes 26a.

On the other hand, as shown in FIGS. 9 and 11,
The windings 22 and 24 are wound counterclockwise from the inside to the outside. The outer ends of the windings 22 and 24 are arranged at the left side of the bulging portion 20b of the insulating layer 20. At the position where the outer ends of the windings 22 and 24 are arranged, the three insulating layers 20 and the windings 22 and 2 are arranged.
A through hole 26b penetrating 4 is formed. Each of the outer ends of the windings 22 and 24 has a through hole 26.
They are electrically connected to each other via b.

As shown in FIGS. 8 to 11, the winding 2
Inner ends of 1 to 24 are arranged at positions overlapping with each other. Through holes 28 penetrating the three insulating layers 20 and the windings 21 to 24 are formed at the positions where the inner ends of the windings 21 to 24 are arranged. Winding 21-
The inner ends of 24 are electrically connected to each other through the through holes 28.

In this way, the winding 21 and the winding 23 are connected in parallel, and the winding 22 and the winding 24 are also connected in parallel. The windings 21 and 23 and the windings 22 and 24 are connected in series. Therefore, when all the windings 21 to 24 have 5 turns, the windings 21 to 24 form a winding of 10 turns.

As shown in FIG. 6, the through hole 26
For example, the terminal 27 is inserted into a and 26b.

Further, as shown in FIG. 7, the E-shaped core 2
5A and 25B, the central protrusions are the holes 20 of the insulating layer 20.
It is arranged so as to be butted through a.

The winding wire 21 and the winding wire 22 may be formed by etching each conductor layer in a double-sided printed board in which conductor layers are formed on both surfaces of an insulating substrate. Winding 2
3 and winding 24 may be formed in a similar manner. In this case, the windings 21 to 24 and the insulating layer 20 are stacked by stacking two double-sided printed boards with the insulating layer 20 interposed therebetween.
Can be formed. Alternatively, winding 22
And the winding 23 are formed by etching each conductor layer in the double-sided printed board, and the single-sided printed board is laminated on the upper and lower sides of the double-sided printed board with the insulating layer interposed therebetween. You may form the laminated body of windings 21-24 and the insulating layer 20 by etching each conductor layer of a board | substrate and forming the winding 21 and the winding 24. Alternatively, the conductor plate is punched out to form the windings 21 to 2.
4 may be formed and these are laminated via an insulating layer such as a polyimide film to form a laminated body of the windings 21 to 24 and the insulating layer 20. In addition, the windings 21 to 24 and the insulating layer 2 are formed by a thin film forming technique such as a sputtering method.
You may form the laminated body of 0.

In the planar coil according to this embodiment,
The windings 21 to 24 are the windings 1 in the first embodiment.
As in the case of 1, the inner radius of the n-th winding portion including the N-turn winding portion is r _i (n) and the outer radius is r _o (n). Inner radius r _min , difference W between outer radius of outermost winding part and inner radius of innermost winding part
r _i (n) and r _o (n) are minimized so that the value of A represented by the equation (1) is minimized when _total and the distance D between the winding portions between adjacent turns are given. Has been defined.

Other configurations, operations and effects in this embodiment are the same as those in the first embodiment.

[Third Embodiment] Next, the third embodiment of the present invention will be described.
The configuration of the flat transformer according to the embodiment will be described. 13 is a plan view of the plane transformer according to the present embodiment, FIG. 14 is a right side view of the plane transformer shown in FIG.
FIG. 15 is a sectional view taken along line CC in FIG. As shown in these drawings, the planar transformer according to the present embodiment is composed of conductor patterns formed of flat conductors including foils, and has four windings 31 to 31 stacked in the thickness direction. 34, three insulating layers 30 arranged between the windings, and E-shaped cores 35A and 35B mounted on a laminated body of the windings 31 to 34 and the insulating layer 30. Copper, for example, is used as the conductor. Windings 31 to 3
4 corresponds to the "plurality of windings formed in a plane and stacked in the thickness direction" in the present invention.

FIG. 16 is a plan view showing the uppermost winding 31 and the insulating layer 30 therebelow, and FIG. 17 is the second winding 3 from the top.
2 is a plan view showing the insulating layer 30 therebelow, FIG. 18 is a plan view showing the third winding 33 from the top and the insulating layer 30 below it, and FIG. 19 is a plane showing the winding 34 at the bottom layer. 20 and 20 are plan views showing the insulating layer 30.

As shown in FIG. 20, the insulating layer 30 has a substantially disk shape. A circular hole 30a is formed in the central portion of the insulating layer 30. Further, the insulating layer 30 has bulging portions 30b, 3 in which a part of the outer peripheral portion bulges outward in the radial direction.
It has 0c. The bulging portions 30b and 30c have holes 30a.
They are arranged at positions symmetrical to each other as the center. Each of the windings 31 to 34 is arranged in a region between the outer peripheral portion of the hole 30a and the outer peripheral portion of the insulating layer 30. Although not shown in FIG. 20, a through hole 38 described later is formed in the insulating layer 30 arranged between the windings 32 and 33.

As shown in FIGS. 16 and 19, each of the windings 31 and 34 is a one-turn winding. One end of each of the windings 31 and 34 has an insulating layer 30.
The bulging portion 30c is arranged at the right side position.
At the position where one ends of the windings 31 and 34 are arranged, 3
A through hole 39a is formed so as to penetrate the one insulating layer 30 and the windings 31 and 34. One ends of the windings 31 and 34 are electrically connected to each other through the through hole 39a. Further, the other ends of the windings 31 and 34 are arranged at positions on the left side of the bulging portion 30c of the insulating layer 30. At the position where the other ends of the windings 31 and 34 are arranged, the three insulating layers 30 and the windings 31 and 3 are provided.
A through hole 39b penetrating 4 is formed. The other ends of the windings 31 and 34 are electrically connected to each other through the through hole 39b. Therefore, winding 3
1, 34 are connected in parallel.

On the other hand, as shown in FIGS. 17 and 18, each of the windings 32 and 33 is composed of a conductor pattern formed by spirally arranging flat conductors including foils. . The windings 32 and 33 are N-turn (N is an integer of 2 or more) windings. In FIGS. 17 and 18, as an example, the windings 32 and 3 of 5 turns are provided.
3 is shown.

As shown in FIG. 17, the winding 32 is wound counterclockwise from the inside to the outside. The outer end of the winding 32 has a bulge 30 of the insulating layer 30.
It is located at the left side in b. This winding 32
At the position where the outer end of the
And a through hole 36b penetrating the winding 32 is formed.

As shown in FIG. 18, the winding 33 is wound clockwise from the inside to the outside. Also,
The outer end of the winding 33 is arranged at the right side of the bulging portion 30b of the insulating layer 30. A through hole 36 a is formed at a position where the outer end of the winding 33 is arranged so as to penetrate the three insulating layers 30 and the winding 33.

As shown in FIGS. 17 and 18, the inner ends of the windings 32 and 33 are arranged at positions overlapping with each other. A through hole 38 is formed at a position where the inner ends of the windings 32 and 33 are arranged so as to penetrate the windings 32 and 33 and the insulating layer 30 arranged between them. The inner ends of the windings 32 and 33 are electrically connected to each other through the through holes 38. Therefore, the winding 32 and the winding 33 are connected in series. If each of the windings 32 and 33 has 5 turns,
33 forms a winding of 10 turns.

As shown in FIG. 14, the through hole 36
For example, the terminal 37 is inserted into the a and 36b, and the terminal 40 is inserted into the through hole 39, for example.

Further, as shown in FIG. 15, in the E-shaped cores 35A and 35B, the central convex portions are the holes 3 of the insulating layer 30.
It is arranged so as to be abutted through 0a.

The winding 31 and the winding 32 may be formed by etching each conductor layer in a double-sided printed board in which conductor layers are formed on both surfaces of an insulating substrate. Winding 3
3 and winding 34 may be formed in a similar manner. In this case, the windings 31 to 34 and the insulating layer 30 are formed by stacking two double-sided printed boards with the insulating layer 30 interposed therebetween.
Can be formed. Alternatively, the winding 32
And the winding 33 are formed by etching each conductor layer in the double-sided printed board, and the single-sided printed board is laminated on the upper and lower sides of the double-sided printed board with the insulating layer interposed therebetween. A laminated body of the windings 31 to 34 and the insulating layer 30 may be formed by etching the conductor layers of the substrate to form the windings 31 and 34. Alternatively, the conductor plate is punched out to form the windings 31 to 31.
4 may be formed and these are laminated via an insulating layer such as a polyimide film to form a laminated body of the windings 31 to 34 and the insulating layer 30. In addition, the windings 31 to 34 and the insulating layer 3 are formed by a thin film forming technique such as a sputtering method.
You may form the laminated body of 0.

In the flat transformer according to the present embodiment, one of the windings 31 and 34 and the windings 32 and 33 serves as a primary winding, and the other serves as a secondary winding.

In the flat transformer according to the present embodiment, the windings 32 and 33 include an N-turn winding portion, like the winding 11 in the first embodiment.
The inner radius of the turn winding part is r _i (n) and the outer radius is r _o (n)
And the inner radius r _{min of} the innermost winding portion, the difference W _total between the outer radius of the outermost winding portion and the inner radius of the innermost winding portion, and between the winding portions between adjacent turns. R _i (n) and r _o (n) are determined so that the value of A represented by the equation (1) becomes minimum when the distance D is given.

Other configurations, operations and effects in this embodiment are the same as those in the first embodiment.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made. For example, the number of turns of the winding and the number of windings are not limited to those shown in the embodiment, and can be set arbitrarily.

The present invention can also be applied to a planar transformer in which a part of the plurality of windings is formed of a conductor other than a flat plate, for example, a round wire conductor.

[0075]

As described above, according to the plane coil according to claim 1 or 2 or the plane transformer according to claim 3, r _{i is set} so that the value of A represented by the formula (1) is minimized. By setting (n) and r _o (n), the winding can be arranged so that the loss is minimized in the limited space, and as a result, the loss due to the resistance of the conductor can be reduced. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a plan view of a planar coil according to a first embodiment of the present invention.

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

FIG. 3 is a plan view of a planar coil of a first comparative example.

FIG. 4 is a plan view of a planar coil of a second comparative example.

FIG. 5 is a plan view of a planar coil according to a second embodiment of the present invention.

FIG. 6 is a right side view of the planar coil shown in FIG.

7 is a sectional view taken along line BB in FIG.

FIG. 8 is a plan view showing an uppermost winding and an insulating layer thereunder in a planar coil according to a second embodiment of the present invention.

FIG. 9 is a plan view showing a second winding from the top and an insulating layer therebelow in the planar coil according to the second embodiment of the invention.

FIG. 10 is a plan view showing a third winding from the top and an insulating layer thereunder in the planar coil according to the second embodiment of the invention.

FIG. 11 is a plan view showing a lowermost layer winding in the planar coil according to the second embodiment of the present invention.

FIG. 12 is a plan view showing an insulating layer in a planar coil according to a second embodiment of the present invention.

FIG. 13 is a plan view of a flat transformer according to a third embodiment of the present invention.

14 is a right side view of the plane transformer shown in FIG.

15 is a cross-sectional view taken along the line CC in FIG.

FIG. 16 is a plan view showing a winding of the uppermost layer and an insulating layer thereunder in a flat transformer according to a third embodiment of the present invention.

FIG. 17 is a plan view showing a second winding from the top and an insulating layer therebelow in the flat transformer according to the third embodiment of the present invention.

FIG. 18 is a plan view showing a third winding from the top and an insulating layer thereunder in a planar transformer according to a third embodiment of the present invention.

FIG. 19 is a plan view showing a lowermost layer winding in the planar transformer according to the third embodiment of the present invention.

FIG. 20 is a plan view showing an insulating layer in a flat transformer according to a third embodiment of the present invention.

[Explanation of symbols]

10 ... Insulating layer, 11 ... Winding wire, 12 ... Through hole.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01F 27/28 H01F 19/00 H01F 30/00

Claims (3)

(57) [Claims] 1. A flat coil having a winding formed by arranging flat conductors in a spiral shape, wherein the winding includes a winding portion of N turns (N is an integer of 2 or more). , N turns from the inside (n is an integer of 1 or more and N or less)
The radius of the inner circumference of the eye winding part is r _i (n), the radius of the outer circumference is r _o (n), the radius r _min of the inner circumference of the innermost winding part, and the outermost winding When the difference W _total between the radius of the outer peripheral portion of the portion and the radius of the inner peripheral portion of the innermost winding portion and the distance D between the winding portions between adjacent turns are given, Equation (1) A planar coil characterized in that r _i (n) and r _o (n) are defined such that the value of A represented is the minimum. [Equation 1] (However, r _i (1) = r _min , r _i (n + 1) −r _o (n) = D, r _o
(N) -r _i (1) = W _total ) 2. The plurality of windings are provided, and the plurality of windings are stacked in the thickness direction via an insulating layer and are connected in parallel or in series. Plane coil. 3. A plurality of windings formed in a plane and stacked in a thickness direction and an insulating layer arranged between the respective windings, wherein some of the plurality of windings are provided. Becomes the primary winding,
A planar transformer in which some of the other windings of the plurality of windings are secondary windings, and at least one of the plurality of windings has a flat conductor arranged in a spiral shape. Including a winding portion of N turns (N is an integer of 2 or more) formed by
The radius of the inner circumference of the (third, integer less than or equal to N) th winding part
_i (n), the outer radius is r _o (n), the inner radius r _min of the innermost winding portion, the outer radius of the outermost winding portion and the innermost winding portion Difference W from the inner radius of
r _i (n) and r _o (n) are minimized so that the value of A represented by the equation (1) is minimized when _total and the distance D between the winding portions between adjacent turns are given. A flat transformer characterized by being defined. [Equation 2] (However, r _i (1) = r _min , r _i (n + 1) −r _o (n) = D, r _o
(N) -r _i (1) = W _total )