JPH05226155A - Planar structure transformer and inductor coil - Google Patents

Abstract

PURPOSE:To minimize a copper loss under limited spatial restrictions and to make generation of heat uniform in all places in regard to a coil for a planar structure transformer and an inductor coil which is suitable for a high-frequency operation. CONSTITUTION:A plurality of doughnut-shaped coils l of a planar structure are so disposed on a plane as to share the center with one another, a cut part 1a is provided in each of the coils 1, the coils 1 are connected in series by connecting parts 4 and thereby a coil part having a desired number of turns is formed. The respective widths W1 to Wi of these coils 1 are made to have values computed by a computation formula which is determined in accordance with the width Ws and the number of turns of the whole of the coil part so that a copper loss of each of the coils 1 be the same value as others, and the widths are made larger as the coils become more distant from the center. According to this constitution, the copper loss of the coil part is made uniform in all places under limited spatial restrictions and the loss of the coil part is made small.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil having a planar structure which constitutes a transformer and an inductor suitable for high frequency operation.

[0002]

2. Description of the Related Art In recent years, miniaturization of integrated circuits has made electronic circuits smaller and lighter, and miniaturization is an essential issue in switching converters that can obtain high-quality electric power. The conversion frequency of the switching power supply is increasing year by year because it is effective to miniaturize the switching power supply by increasing the conversion frequency and reducing the size of the magnetic parts. However, if the coil of the magnetic component is composed of a magnet wire with a circular cross section, copper loss will increase due to eddy currents generated by high frequency operation, and heat generation due to copper loss will be dissipated, which will hinder miniaturization of the magnetic component. The problem arises that Therefore, a coil having a planar structure in which the thickness of the conductor is set to the depth of the skin is devised to reduce the eddy current generated by the high frequency operation.

An example of designing a coil of this planar structure for a transformer and an inductor is described in A. F. Goldber
g, J. G. Kassakian, M .; F. Schle
The paper "Issues Related
to 1-10-MHZ Transformer D
design "(IEEE Trans. PowerEl
electronics, Vol. 4, No. 1, pp. 1
13-123, January, 1989).

The above-mentioned paper shows the distribution of copper loss when a donut coil as shown in the structural diagrams of FIGS. 4A and 4B is wound 6 turns. In FIG. 4, (a)
Shows a top view, and (b) shows a sectional view of a half part.
1 is a coil having a planar structure, 2 is a core, 3 is an insulator, 4
Indicates a connecting portion. The coil 1 is formed in a donut shape, and a plurality of the coils 1 are arranged in a plane so as to share the center,
A coil portion is formed. Further, the coil portion is covered with the insulator 3 and surrounded by the core 2. Conventionally, the width of each of these donut-shaped coils 1 has been made to be the same value for both the coil 1 arranged inside and the coil 1 arranged outside. Then, in order to prevent the doughnut-shaped coil 1 from becoming a short coil, a cutting portion 1a is provided in a part of each coil 1, and the inner and outer coils 1 are connected in series by the connecting portion 4 near the cutting portion 1a, The number of coils 1 connected in series was changed to produce a coil portion having a desired number of turns.

[0005]

However, in the case where the planar structure transformer and the inductor coil are constructed by the above-mentioned prior art, the resistance of the donut-shaped coil 1 arranged on the outer side is the resistance of the donut-shaped coil arranged on the inner side. Since the resistance is higher than the resistance of No. 1, the inner and outer coils 1 have different copper losses, and there is a problem that heat generation becomes non-uniform. Also, the fact that the copper loss of the planar structure transformer and the inductor coil differs depending on the location does not comply with the law of nature that requires the uniformity of loss, so that the copper loss of the entire coil section should be minimized. There was a problem that it was not designed.

The present invention has been made to solve the above problems, and its object is to provide a planar structure transformer having a minimum copper loss under a limited space constraint and a uniform heat generation everywhere. It is to provide a coil for an inductor.

[0007]

In order to achieve the above object, the planar structure transformer and inductor coil of the present invention comprises a plurality of series-connected donut-shaped windings or spiral windings sharing a center. It is characterized in that the copper loss of each portion of the winding is increased according to a calculation formula that becomes the same value as the width of the winding becomes farther from the center, or substantially according to the calculation formula.

[0008]

In the planar structure transformer and inductor coil of the present invention, the width of the plurality of donut-shaped windings sharing the center is increased as the distance from the center increases. That is, the width of the doughnut-shaped windings in order to make the copper loss the same,
Use the value calculated using the formula to obtain the same copper loss for each winding, and make the copper loss uniform throughout the coil under limited space restrictions to reduce the loss in the coil. ing.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a top view showing the structure of an embodiment of the present invention. In the figure, 1 is a coil having a planar structure, 4 is a connecting portion, W1 is the width of the innermost coil 1, W2, W3 ... Wi.
Is the width of the outer coil 1, Ws is the width of the entire coil, D is the insulation distance between the coils, and R is the innermost coil 1.
Is the inner radius of.

The coil 1 is formed in a donut shape, and a plurality of coils 1 are arranged in a plane so that their diameters are changed so as to share the center.
Each coil 1 has a cut portion 1a, and one end of the coil 1 in the cut portion 1a is connected in series to one end of the coil 1 in the cut portion 1a of another adjacent coil 1 via the connection portion 4 to make a predetermined turn. A coil portion for several tunnels or inductors is formed. In this embodiment, the width W1, W2, W of each doughnut-shaped coil 1 is set so that the copper loss is minimized and the heat generation is uniform under the limited space constraints.
3, ... Wi is increased as it moves away from the center according to the following calculation formula.

Here, the width of each coil 1 is determined as follows, assuming that the number of turns of the coil portion is 2 to 10 turns. The distance between a point on the outer circumference of the outermost coil 1 and a point where a perpendicular line drawn from this point toward the center intersects with the inner circumference of the innermost coil 1 is W _S ,
The distance between the point on the outer circumference and the point on the inner circumference of each coil 1 that intersects this perpendicular is W1 to Wi (i is an integer of 2 or more and 10 or less indicating the number of turns of the coil) in order from the inside of the concentric circle,
When the distance between a point on the inner circumference of the innermost coil 1 and the center of the circle is R, and the insulation distance between windings provided for insulation between the coils is D, W1 is the coil portion. Depending on the number of turns (the number of turns), it is set so as to satisfy any of the expressions (1) to (9), and other than W1 is determined by the expression (10).

(Conditional expression for 2 turns) W1 ² / R + (2 + D / R) W1 = W _S (1) (Condition expression for 3 turns) W1 ³ / R ² + (D / R ² +3) / R) W1 ² + (3D / R +
_{3) W1 = W S ... (} 2) (4 condition in the case of the ^{turn) W1 4 / R 3 + (} D / R 3 + 4 / R 2) W1 3 + (4D / R 2
^{+ 6 / R) W1 2 +} (6D / R + 4) W1 = W S ...
(3) (conditional expression for 5 turns) W1 ⁵ / R ⁴ + (D / R ⁴ + 5 / R ³ ) W1 ⁴ + (5D / R ³
+ 10 / R ² ) W1 ³ + (10D / R ² + 10 / R) W1 ²
+ (10D / R + 5) W1 = W S ... (4) ( conditional expression in the case of 6 ^{turns) W1 6 / R 5 + (} D / R 5 + 6 / R 4) W1 5 + (6D / R 4
+ 15 / R ³ ) W1 ⁴ + (15D / R ³ + 20 / R ² ) W1
³ + (20D / R ² + 15 / R) W1 ² + (15D / R +
6) W1 = W _S (5) (conditional expression for 7 turns) W1 ⁷ / R ⁶ + (D / R ⁶ + 7 / R ⁵ ) W1 ⁶ + (7D / R ⁵
+ 21 / R ⁴ ) W1 ⁵ + (21D / R ⁴ + 35 / R ³ ) W1
⁴ + (35D / R ³ + 35 / R ² ) W1 ³ + (35D / R <sup>2
+ 21 / R) W1 2 +</sup> (21D / R + 7) W1 = W S ...
(6) (Conditional expression for 8 turns) W1 ⁸ / R ⁷ + (D / R ⁷ + 8 / R ⁶ ) W1 ⁷ + (8D / R ⁶
+ 28 / R ⁵ ) W1 ⁶ + (28D / R ⁵ + 56 / R ⁴ ) W1
⁵ + (56D / R ⁴ + 70 / R ³ ) W1 ⁴ + (70D / R ³
+ 56 / R ² ) W1 ³ + (56D / R ² + 28 / R) W1 ²
+ (28D / R + 8) W1 = W _S (7) (conditional expression for 9 turns) W1 ⁹ / R ⁸ + (D / R ⁸ + 9 / R ⁷ ) W1 ⁸ + (9D / R ⁷
+ 36 / R ⁶ ) W1 ⁷ + (36D / R ⁶ + 84 / R ⁵ ) W1
⁶ + (84D / R ⁵ + 126 / R ⁴ ) W1 ⁵ + (126D /
R ⁴ + 126 / R ³ ) W1 ⁴ + (126D / R ³ + 84 / R
² ) W1 ³ + (84D / R ² + 36 / R) W1 ² + (36D
/ R + 9) W1 = W S ... (8) ( conditional expression in the case of 10 ^{turns) W1 10 / R 9 + (} D / R 9 + 10 / R 8) W1 9 + (10D
/ R ⁸ + 45 / R ⁷ ) W1 ⁸ + (45D / R ⁷ + 120 / R
^{6) W1 7 + (120D /} R 6 + 210 / R 5) W1 6 +
(210D / R ⁵ + 252 / R ⁴ ) W1 ⁵ + (252D /
R ⁴ + 210 / R ³ ) W1 ⁴ + (210D / R ³ + 120 /
R ² ) W1 ³ + (120D / R ² + 45 / R) W1 ² + (4
5D / R + 10) W1 = W S ... (9) W K = W1 [R + W1 ... + W K-1 + (K-1) D] / R
(However, K = 2 to 10) (10) The operation of the embodiment configured as described above will be described.

In this embodiment, in order to minimize the copper loss of the planar structure transformer and the inductor coil, the formula for calculating the copper loss of the plurality of donut-shaped coils 1 sharing the center is derived in the range of 2 to 10 turns. To do. At this time, the width of the radial cut portion 1a provided in a part of the donut-shaped coil 1 is sufficiently smaller than the average peripheral circuit of the winding of the donut-shaped coil 1. Then, the width of the outer coil 1 is displayed using the width of the inner coil 1 by utilizing the relationship that the copper loss of the outer coil 1 is equal to the copper loss of the inner coil 1. This relationship is the expression (10). The width W of the innermost coil 1 can be obtained from equations (1) to (9) according to the width of the entire coil portion and the number of turns.

Equations (1) to (9) are expressed by the width W1 of the innermost coil 1, the insulation distance D between windings provided for insulation between the coils, the inner radius R of the innermost coil 1, and the coil It gives the relation of the width Ws of the whole part, and is a high-order equation regarding W1. W1 up to 4 turns of the coil can be obtained by algebraically solving a quartic equation, but W1 of 5 turns or more cannot be obtained algebraically. Therefore, in order to obtain W1 when the number of turns is 5 turns or more, numerical calculation such as the Newton method or the Bearstow method is used. From W1 obtained in this way, W2 (, W3,
The width of each coil 1 is obtained in the order of ..., W10). By designing the widths of the planar structure transformer and the inductor coil according to the above procedure, it is possible to obtain a coil having a minimum copper loss and a uniform coil where heat is generated under limited space constraints.

Next, the effects of this embodiment will be described with reference to a concrete manufacturing example of the above embodiment.

FIG. 2 is a top view of a planar structure transformer and an inductor coil showing a first manufacturing example according to the embodiment of the present invention. In this figure, the number of turns of the coil portion is 2, the distance D provided for insulation in each coil 1 is 0.01 cm, the inner radius R of the innermost donut-shaped coil 1 is 1 cm, and the width Ws of the entire coil portion is It is set to 5 cm. Substituting this condition into equation (1) to obtain W1,
1 is 1.44 cm. Furthermore, by the formula (10), W
Obtaining 2 gives 3.55 cm. W1 and W2 are 2.
The resistance of the coil in the conventional case designed to be equal to 5 cm and the resistance of this manufacturing example are compared with those of Ansoft (Pittsb, USA).
urg) finite element method resistance calculation program DC
When calculated by the Condition Solver, the resistance of the coil according to the embodiment of the present invention is 70% that of the conventional example.
It has been reduced to%.

FIG. 3 is a top view of a planar structure transformer and an inductor coil showing a second manufacturing example according to this embodiment. In this figure, the number of turns of the coil is 3 turns,
The separation distance D provided for insulation in each coil is 0.01c.
m, the inner radius R of the innermost donut coil is 1 cm,
The width Ws of the entire coil portion is 5 cm. Substituting this condition into the equation (2) to obtain W1, W1 is 0.82c.
m. Further, when W2 and W3 are obtained by the equation (10), W2 is 1.47 cm and W3 is 2.69 cm. The resistance of the coil and the resistance of this embodiment in the conventional case in which W1 to W3 are designed to be equal to 1.66 cm are Ansof.
DC Calculation S, a resistance calculation program by the finite element method of the t company (Pittsburgh, USA)
When calculated by the solver, the resistance of the coil according to the embodiment of the present invention is reduced to 82% of that of the conventional example.

As described above, two manufacturing examples of the embodiment of the present invention have been shown, but it is found that the expressions (3) to (9) derived by the same method as the calculation expression of this embodiment are similarly effective. it is obvious. Further, although the present embodiment shows the case where the coil is a perfect circle, the present invention can be applied even if the coil has a somewhat distorted shape such as a spiral coil by equivalently matching the radius and circumference with the perfect circle. Needless to say. As described above, the present invention can be applied in various ways in accordance with the gist thereof and can take various embodiments.

[0020]

As is apparent from the above description, according to the planar structure transformer and inductor coil of the present invention, the copper loss is minimum and the heat generation is uniform under the limited space constraint. Can be obtained.

[Brief description of drawings]

FIG. 1 is a top view showing an embodiment of the present invention.

FIG. 2 is a top view showing a specific manufacturing example according to the above embodiment.

FIG. 3 is a top view showing another specific manufacturing example according to the above embodiment.

4A and 4B are structural views showing a conventional technique.

[Explanation of symbols]

 1 ... Coil, 1a ... Sectional view, 4 ... Connection part.

Claims (1)

[Claims] 1. A plurality of series-connected toroidal windings or spiral windings sharing a center, wherein the copper loss of each portion of the windings is the same as the width of the winding becomes farther from the center. A coil for a planar structure transformer and inductor, which is increased according to or substantially in accordance with a calculation formula having a value.