JP7288651B2 - planar transformer - Google Patents

Description

Article 30, Paragraph 2 of the Patent Act applies Research at the "Magnetics Study Group (Theme: Power Magnetics, General Magnetic Applications)" sponsored by the Institute of Electrical Engineers of Japan held at the Kinosaki Health and Welfare Center in Toyooka City on March 9, 2018 Published in the meeting materials (date of issue: March 9, 2018) and announced at the study meeting

Article 30, Paragraph 2 of the Patent Act applies Digest Book at "2018 Intermag Conference" hosted by The IEEE Magnetics Society held at Marina Bay Sands Convention Center on April 27, 2018 (website publication date: 2018 April 13) and presented at the same conference

Application of Article 30, Paragraph 2 of the Patent Act May 23, 2018 The 30th ``Dynamics Related to Electromagnetic Force'' Symposium (SEAD30) hosted by the Institute of Electrical Engineers of Japan (Industrial Application Division) held at the Nagano City Lifelong Learning Center ” (published on May 23, 2018) and presented at the symposium

Application of Article 30, Paragraph 2 of the Patent Law The BOOK OF ABSTRACTS (website publication date of : January 4, 2019) and announced at the same conference

Application of Article 30, Paragraph 2 of the Patent Act At the "Wireless Power Transmission Study Group (Theme: Power Conversion Technology, Wireless Power Transmission, General)" hosted by the Institute of Electronics, Information and Communication Engineers held at Kyoto University on October 4, 2018 Disclosed in the technical research report (published on the website: September 26, 2018) and presented at the conference

The present disclosure relates to high efficiency and compact planar transformers for switching power supply applications such as in DC-DC converters.

In general, a transformer has a larger volume than other elements that constitute a switching power supply, and is a factor in increasing the size of the power supply. Therefore, in recent years, a conductor-embedded planar transformer (hereinafter referred to as an embedded transformer) has been proposed (Patent Document 1). In this document, not only is the transformer configured in a planar shape, but the primary coil conductor and the secondary coil conductor are stacked in a spiral manner in a state in which they are vertically superimposed and opposed to each other, and the primary coil conductor and the secondary coil conductor By interposing a non-magnetic insulator between the coil conductor and enclosing part or all of it with a magnetic material, the leakage magnetic flux component generated by the coil that interlinks with the magnetic material is reduced, and the magnetic material The effective resistance due to the loss component of the relative magnetic permeability is reduced.

Also, the conductor-embedded planar transformer has a configuration in which a thin-film primary coil conductor and a thin-film secondary coil conductor are provided on both sides of the non-magnetic substrate, each coil is covered with a magnetic film, and the magnetic films on both sides of the substrate are coupled through vias. By doing so, a technique for reducing AC loss has also been proposed (Patent Document 2)

Not limited to transformers, reduction in inductance and Q value can be reduced by covering part or the entire surface of a planar coil with a non-magnetic insulating layer having a predetermined thickness ratio with respect to the coil wire spacing, and further covering the entire surface with a magnetic material. A technique for improving the allowable current of the coil has already been disclosed (Patent Document 3).

JP-A-5-258958 JP-A-10-74626 Japanese Patent Application Laid-Open No. 2002-299121

However, in order to increase the occupancy rate of the coil, the conventional planar transformer has to have a rectangular cross-sectional shape, and as a result, the skin effect appears remarkably. Furthermore, as the space factor of the coil increases, the distance between the windings becomes closer, so the AC resistance due to the proximity effect also increases.

A planar transformer of the present disclosure is a planar transformer having a flat or thin-film primary coil conductor and a secondary coil conductor laminated on the primary coil conductor, wherein the primary coil conductor and the secondary coil conductor are interposed between the primary coil conductor and the secondary coil conductor. a non-magnetic insulating layer; a first non-magnetic insulating material at the center of the surface of the primary coil conductor opposite to the non-magnetic insulating layer; A second nonmagnetic insulator is provided in the in-plane central portion, and the nonmagnetic insulating layer, the primary coil conductor, the secondary coil conductor, the first nonmagnetic insulator, and the second coil conductor are further provided. Both ends and both side surfaces of the first nonmagnetic insulator side surface of the primary coil conductor, and the second nonmagnetic insulator side of the secondary coil conductor The magnetic body is in contact with the primary coil conductor and the secondary coil conductor and covers the primary coil conductor and the secondary coil conductor at both ends and both side surfaces of the surface of (1 ) .

The thickness of the first non-magnetic insulator in the direction perpendicular to the surface of the primary coil conductor may be 0.8 times or more the width of the primary coil conductor, and the thickness of the second non-magnetic insulator The thickness of the secondary coil conductor in the direction perpendicular to the plane may be 0.8 times or more the width of the secondary coil conductor.

The width of the first nonmagnetic insulator may be 0.6 to 0.8 times the width of the primary coil conductor, and the width of the second nonmagnetic insulator may be the width of the secondary coil conductor. 0.6 to 0.8 times.

A composition of the nonmagnetic insulating layer, the first nonmagnetic insulator, and the second nonmagnetic insulator may be air.

1A and 1B are top and cross-sectional views of an embodiment of the present disclosure; Operation explanatory diagram of one embodiment of the present disclosure A configuration diagram showing simulation conditions of Example 1 of the present disclosure Graph showing simulation results of Example 1 of the present disclosure Configuration diagram showing simulation conditions of Example 2 of the present disclosure and a comparative example Gray scale diagram showing simulation results of Example 2 of the present disclosure and Comparative Example Graph showing simulation results of Example 2 and Comparative Example of the present disclosure An overall view, a circuit diagram, and a cross-sectional view of Example 3 of the present disclosure Appearance view and cross-sectional view of Example 3 of the present disclosure An overall view, a circuit diagram, and a cross-sectional view of Example 4 of the present disclosure External view and cross-sectional view of Example 4 of the present disclosure Overall view, circuit diagram, and cross-sectional view of Example 5 of the present disclosure Appearance view and cross-sectional view of Example 5 of the present disclosure Overall view, circuit diagram, and cross-sectional view of Example 6 of the present disclosure Exterior view and cross-sectional view of Example 6 of the present disclosure

Hereinafter, embodiments according to one aspect of the present disclosure will be described in detail with reference to the drawings. FIG. 1 shows a top view (upper) and a half cross-sectional view (lower) taken along line AA' of the planar transformer (1) in this embodiment. The planar transformer (1) in FIG. 1 has a cylindrical shape. In FIG. 1, 11 and 12 are magnetic bodies. The magnetic bodies 11 and 12 may be formed by laminating preformed solids as described later, or may be integrally formed by solidifying a fluid magnetic composite material or the like.

Reference numerals 21 and 22 denote a primary coil conductor and a secondary coil conductor, respectively, which are made of, for example, spiral flat or thin film conductors. A nonmagnetic insulating layer 34 is provided between the primary coil conductor 21 and the secondary coil conductor 22 . The material is not particularly limited as long as it can maintain sufficient insulation at the voltage used, and may be oil paper, resin, ceramic, air, or the like. In the present embodiment, nonmagnetic insulating layer 34 has the same width as primary coil conductor 21 and secondary coil conductor 22 and is provided along primary coil conductor 21 and secondary coil conductor 22 .

Furthermore, in FIG. 1, non-magnetic insulators 31 and 32 are provided on the surfaces of the primary coil conductor 21 and the secondary coil conductor 22, respectively, in the plane opposite to the non-magnetic insulating layer 34. As shown in FIG. The material of the non-magnetic insulators 31 and 32 is not particularly limited, and may be, for example, resin, ceramic, or air (void). "Provided in the plane" of the coil conductor surface means, in other words, that the widths of the non-magnetic insulators 31 and 32 are formed narrower than the widths of the primary coil conductor 21 and the secondary coil conductor 22. . However, if it is too narrow, the effect will not be obtained, so as to the specific dimension, it is preferable to be about 0.6 to 0.8 times the size of the coil conductor, as will be shown in the examples described later. Also, the thickness of the non-magnetic insulators 31 and 32 (the length in the direction perpendicular to the surfaces of the primary coil conductor 21 and the secondary coil conductor 22) should be as large as possible within the limitations of the shape and dimensions of the planar coil 1. . Preferably, the width is 0.8 times or more the width of the primary coil 21 and the secondary coil 22, as shown in the examples described later.

Furthermore, the primary coil conductor 21 , secondary coil conductor 22 , nonmagnetic insulating layer 34 , nonmagnetic insulator 31 , and nonmagnetic insulator 32 are covered with magnetic bodies 11 and 12 . The magnetic bodies 11 and 12 may be magnetic bodies such as ferrite molded in advance from the shape of the object to be coated. Alternatively, it may be molded by pouring a composite magnetic material around the object to be coated. When the non-magnetic insulators 31 and 32 are air, a thin cover may be provided in advance to protect the gap so that the composite material does not flow into the gap.

FIG. 2 shows the operation and effects of this embodiment shown in FIG. FIG. 2 shows cross sections of the primary coil conductors 21 and 22, the nonmagnetic insulating layer 34, and the nonmagnetic insulators 31 and 32 in the innermost turns. In addition, FIG. 2 shows an example of magnetic lines of force generated on the inner peripheral side of the coil (solid curves in the figure). Magnetic lines of force are generated when a current flows through a coil of an arbitrary winding. The magnetic lines of force emitted by (21, 22) received a force drawn toward the outer circumference from the coil on the outer circumference (broken curve in the figure). When the magnetic lines of force are strongly attracted to the outer circumference, some of the magnetic lines of force on the inner circumference enter the conductor of the coil, generating eddy currents. As a result, AC resistance will increase. On the outermost winding, on the contrary, a phenomenon occurs in which the lines of magnetic force are attracted toward the inner circumference.

Therefore, in the present embodiment, non-magnetic insulators 31 and 32 are provided on the upper surface of the coil, which is the path of the lines of magnetic force. Then, the lines of magnetic force attempt to move upward on the paper to avoid the non-magnetic insulators 31 and 32 . Therefore, even if the magnetic field lines are attracted to the outer peripheral side, the number of magnetic lines of force that enter the coil conductor is greatly reduced. As a result, conventional methods such as a type without the magnetic layers 11 and 12 and a type in which the primary coil conductor 21 and the secondary coil conductor 22 are directly covered with the magnetic materials 11 and 12 without providing the non-magnetic insulators 31 and 32 are available. It is possible to realize a planar transformer that has less AC resistance than a planar transformer, in other words, that has a high inter-coil efficiency.

Examples of the present disclosure will be described below.
(Example 1)
In this embodiment, parameter analysis of the non-magnetic insulators 31 and 32 is performed. FIG. 3 shows the analysis model of this embodiment. In this embodiment, the nonmagnetic insulating layer 34 and the nonmagnetic insulators 31 and 32 are made of air. That is, it has a structure in which there is no magnetic material between the layers of the primary coil conductor and the secondary coil conductor, and voids are provided above the primary coil conductor and below the secondary coil conductor, respectively. .

解析にはＪＳＯＬ社のＪＭＡＧ－Ｄｅｓｉｇｎｅｒ（登録商標）ｖｅｒ．１７．０を用いた。解析方法は二次元軸対称周波数応答解析である。ｚ軸を中心としてｚｒ平面をθ方向に回転させた軸対称モデルを解析モデルとした。平面トランスは外半径８．８ｍｍ、高さ２．５ｍｍの円筒形状とした。一次コイル導体、二次コイル導体ともに巻数Ｎ＝６のスパイラルコイルとし、外半径を８．３ｍｍ、銅箔パターンの幅を０．８ｍｍ、銅箔パターンの厚さを０．１ｍｍ、銅箔パターン間の幅を０．５ｍｍとしている。さらに空隙（Ｖｏｉｄ）（非磁性絶縁体３１、３２）の高さをｈ_ｔ、幅をｗ_ａとし、ｈ_ｔ＝０．１～１ｍｍ、ｗ_ａ＝０．１～０．８ｍｍとした条件で解析を行った。コアである磁性体１１、１２は高周波で低損失な磁性コンポジット材料を想定し複素比透磁率をμ’＝１０、μ” ＝０．１とした。電流はＩ＝１Ａ_ｍａｘ、周波数はＩＳＭバンドである１３．５６ＭＨｚとし、二次側開放時における鉄損を考慮した抵抗Ｒ_ｐ、インダクタンスＬ_ｐ、および二次側短絡時におけるインダクタンスＬ_ｓｈを解析した。 Table 1 shows the analysis conditions in this example.

JMAG-Designer (registered trademark) ver. 17.0 was used. The analysis method is two-dimensional axisymmetric frequency response analysis. An axisymmetric model obtained by rotating the zr plane in the θ direction around the z axis was used as the analysis model. The plane transformer had a cylindrical shape with an outer radius of 8.8 mm and a height of 2.5 mm. Both the primary coil conductor and the secondary coil conductor were spiral coils with the number of turns N = 6, the outer radius was 8.3 mm, the width of the copper foil pattern was 0.8 mm, the thickness of the copper foil pattern was 0.1 mm, and the distance between the copper foil patterns is 0.5 mm. Further, under the conditions that h _t =0.1 to 1 mm and w _a =0.1 to 0.8 mm, the height of the void (the nonmagnetic insulators 31 and 32) is h _t and the width is w _a . I did the analysis. The magnetic bodies 11 and 12, which are the cores, are assumed to be a high-frequency, low-loss magnetic composite material, and the complex relative permeability is set to μ′=10 and μ″=0.1. The current is I=1 A _max and the frequency is the ISM band. is 13.56 MHz, and the resistance R _p , the inductance L _p , and the inductance L _sh when the secondary side is short-circuited are analyzed in consideration of iron loss when the secondary side is open.

ここに、ω：角周波数（ｒａｄ／ｓ）、Ｌ_ｐ：二次側開放時のインダクタンス（Ｈ）、Ｒ_ｐ：二次側開放時の一次側抵抗（Ω）である。さらに結合係数ｋは下式を用いて算出した。

ここに、Ｌ_ｐ：二次側開放時のインダクタンス（Ｈ）、Ｌ_ｓｈ：二次側短絡時のインダクタンス（Ｈ）である。 The Q value of the primary side coil of the transformer was calculated using the following formula.

Here, ω: angular frequency (rad/s), L _p : inductance (H) when the secondary side is open, and R _p : primary side resistance (Ω) when the secondary side is open. Furthermore, the coupling coefficient k was calculated using the following formula.

Here, L _p : inductance (H) when the secondary side is open, L _sh : inductance (H) when the secondary side is short-circuited.

The analysis results are shown below. FIG. 4 shows the impedance characteristics of the planar transformer 1 when μ″=0.1. First, FIG. 4(a) shows the resistance _Rp when the secondary side is open. h _t =0.1→1.0, w _a =0.1→0.7), the amount of magnetic material decreases, the resistance caused by iron loss decreases, and as a result, R _p decreases.

Next, FIG. 4(b) shows the inductance _Lp when the secondary side is open. Since the magnetic material decreases as the air gap increases, L _p (inductance when the secondary side is open) also decreases.

Next, FIG. 4(c) shows the Q value when the secondary side is open. For the Q value, there is an optimum value for the size of the void. In this example, Q exhibits a maximum value of 120.6 when h _t =1.0 and w _a =0.7.

FIG. 4(d) shows the inductance (Laekage inductance) _Lsh when the secondary side is short-circuited. In this case, _Lsh fluctuated by only about 0.03% with respect to the parameter change of the void.

The figure (e) shows the coupling coefficient k. Although the coupling coefficient k tends to decrease as the gap increases, 0.96 or more can be ensured within the parameter range of this example. Overall, the Q value is highest at h _t =1.0, w _a =0.7, h _t =1.0, w _a =0.8 or h _t =1.0, w _a = At 0.6, the Q value is rather lowered. Therefore, it is considered that the inter-coil efficiency is improved by providing an air gap in the range of w _a =0.6 to 0.8.

As described above, according to this embodiment, by providing an air gap (non-magnetic insulator) in the range of h _t = 1 and w _a = 0.6 to 0.8, it is possible to reduce the AC resistance and improve the Q value. It is possible to improve the inter-coil efficiency as a whole.

A second embodiment of the present disclosure will be described below.
(Example 2)
FIG. 5(a) shows a conventional planar transformer (comparative example), and FIG. 5(b) shows an analytical model of the planar transformer according to the present embodiment. In the planar transformer of the comparative example, both the primary coil conductor and the secondary coil conductor are completely embedded in the magnetic material. In the embedded transformer according to this embodiment, no magnetic material is provided between the layers of the primary coil conductor and the secondary coil conductor, and a gap of 1 mm in height and 0.7 mm in width is provided between the upper part of the primary coil conductor and the lower part of the secondary coil conductor. is provided. Furthermore, a magnetic cap structure with a width of 0.05 mm is formed on both ends of the winding.

Table 2 shows the analysis results of the resistance R _p and inductance L _p when the secondary side is open, and the resistance R _sh and inductance L _sh when the secondary side is short-circuited. In Table 2, the upper row (Embedded transformer) is the comparative example, and the lower row (Embedded transformer with MPC) is the analysis result of the present example. Here, MPC is an abbreviation for Magnetic Flux Path Control Technology, and means a technology for controlling magnetic lines of force by appropriately arranging magnetic bodies. In the present embodiment, this is equivalent to the case where air is used as the non-magnetic insulator (no magnetic material is provided at important points). As in Example 1, JMAG-Designer (registered trademark) ver. 17.0 was used.

FIG. 6 shows the current density distribution of the embedded transformer when the secondary side is short-circuited, which is close to the actual operation. In the comparative example ((a) in the figure), the current density is biased toward the ends of the coil, particularly toward the innermost circumference. However, in the present embodiment in which the air gap, which is a non-magnetic insulator, is provided, the current density distribution within the conducting wire is substantially uniform. This is because magnetic flux interlinking with the ends of the rectangular wire is reduced by providing a gap and adopting a magnetic cap structure.

In this embodiment, the resistance _Rp when the secondary side is open is calculated to be 0.32Ω, which is 66.7% lower than the conventional value of 0.96Ω. This is because the magnetic cap structure is formed by providing the air gap, and the magnetic flux interlinking with the end of the copper wire is reduced. It is also conceivable that the resistance is reduced due to iron loss corresponding to the opening of the gap.

In this embodiment, the inductance _Lp when the secondary side is open is 0.45 μH, which is 56.9% of the 1.04 μH of the comparative example. It is considered that this is because the total amount of the magnetic material was reduced by providing the air gap. Furthermore, in this embodiment, the inductance when the secondary side is short-circuited, that is, the leakage inductance _Lsh is 0.03 μH, which is 85.2% of the 0.21 μH of the comparative example. It is considered that this is because the closed magnetic circuit is blocked by providing a gap between the wires of the primary winding and the secondary winding.

図７に（３）式よりコイル間効率η_ｃを算出した結果を示す。本実施例（Ｅｍｂｅｄｄｅｄ ｔｒａｎｓｆｏｒｍｅｒ ｗｉｔｈ ＭＰＣ）ではη_ｃ＝９８．３％になり、比較例（Ｅｍｂｅｄｄｅｄ ｔｒａｎｓｆｏｒｍｅｒ）の９７．６％よりも０．７％向上した。 The inter-coil efficiency in this embodiment will be obtained below. The inter-coil efficiency η _c is obtained as follows using the product of the coupling coefficient k and the Q value.

FIG. 7 shows the result of calculating the inter-coil efficiency _ηc from the equation (3). In this example (embedded transformer with MPC), η _c =98.3%, which is 0.7% higher than 97.6% in the comparative example (embedded transformer).

Summarizing the results of Examples 1 and 2, the maximum Q value was 120.6 when h _t =1 and w _a =0.7. At this time, the current density inside the copper wire was less uneven, so the AC resistance was reduced. In addition, compared to the conventional embedded type comparative example, the magnetic flux interlinking with the end of the coil conductor was reduced, and the open resistance _Rp was reduced by 66.7%. Further, the coupling coefficient k was improved by 7.6% due to the 85.2% reduction in the leakage inductance _Lsh , and finally became 0.965.

When the inter-coil efficiency η _c is obtained from the coupling coefficient k and the Q value, the above example (Embedded transformer with MPC) is 0.7% higher than the comparative example (Embedded transformer), and the loss is 30% lower. In the above examples, it was demonstrated that the efficiency between the coils can be improved by increasing the coupling coefficient k and the Q value.

Another embodiment of the planar transformer 1 having a different shape will be described below.
(Example 3)
FIG. 8 shows an overall view (a), a circuit diagram (b), and a sectional view (c) of the planar transformer 1 of the third embodiment. In this embodiment, the winding ratio is changed between the primary side and the secondary side to provide a step-up function. When the primary and secondary coil conductors face each other with the same number of turns, the step-up ratio is 1:1. has 4 turns (N=), while on the secondary side, the secondary coil conductor 22 and the secondary coil conductor 23 are connected in series (as shown in the circuit diagram (b)), and the number of turns is (N) is substantially 8, and the step-up ratio can be set to 1:2.

FIG. 9 shows the appearance of the planar transformer and the planar shapes of the primary coil conductor and the secondary coil conductor (BB' cross section and CC' cross section, respectively) in this embodiment. The coil on the secondary side is formed by stacking two coils shown in the lower right of the figure, but the wiring for series connection is omitted.

(Example 4)
FIG. 10 shows an overall view (a), a circuit diagram (b), and a sectional view (c) of a planar transformer 1 according to the fourth embodiment, and FIG. Figures (BB' cross section and CC' cross section, respectively) are shown. In this embodiment, the number of turns on the primary side is (N=) 3, and the number of turns on the secondary side is (N=) 2, so the step-up ratio is 3:2 (see FIG. 10(b)). Although the pitch of the coil conductors is different between the primary side and the secondary side, an air gap (non-magnetic insulator) is provided above the primary coil conductor and below the secondary coil conductor.

(Example 5)
FIG. 12 shows an overall view (a), a circuit diagram (b), and a sectional view (c) of a planar transformer 1 according to Example 5, and FIG. Figure shows. This embodiment is characterized by having a meander-shaped coil conductor that is neither spiral nor concentric. By making the coils meandering, the two ends of each coil can be arranged side by side.

(Example 6)
FIG. 14 shows an overall view (a), a circuit diagram (b), and a sectional view (c) of a planar transformer 1 according to Example 6, and FIG. Figure shows. This embodiment relates to a plane transformer of a meandering coil type in which the number of turns is changed between the primary side and the secondary side. In this embodiment, the number of turns on the primary side is (N=) 2, and the number of turns on the secondary side is (N=) 1, so the step-up ratio is 2:1 (see FIG. 14(b)). Although the pitch of the coil conductors is different between the primary side and the secondary side, an air gap (non-magnetic insulator) is provided above the primary coil conductor and below the secondary coil conductor.

As described above, according to the present embodiment, the flat primary coil conductor 21 and the secondary coil conductor 22 are laminated with the nonmagnetic insulating layer (air gap) 34 interposed therebetween, and the nonmagnetic insulating layer of the primary coil conductor 21 A non-magnetic insulator (air gap) 31 is provided on the side opposite to 34, and a non-magnetic insulator (air gap) 32 is provided on the side opposite to the non-magnetic insulating layer 34 of the secondary coil conductor 22. The non-magnetic insulating layer 34 and the primary coil conductor 21, the secondary coil conductor 22, and the non-magnetic insulators 31, 32, a small planar transformer with high inter-coil efficiency can be realized.

In the present embodiment, the non-magnetic insulator is an air gap, but it is not limited to this, and other materials such as resin such as epoxy or ceramics can be used as long as they are non-magnetic and can guarantee insulation. may

INDUSTRIAL APPLICABILITY By applying the present invention to a transformer of a switching power supply, it is possible to achieve miniaturization and high efficiency of equipment. In particular, since the precision coil conductor is covered with a strong magnetic material, it is structurally robust and suitable for applications under harsh conditions such as equipment onboard artificial satellites.

Reference Signs List 1 planar transformer 11, 12 magnetic material 21 primary coil conductor 22, 23 secondary coil conductor 31, 32 nonmagnetic insulator 34 nonmagnetic insulating layer

Claims (4)

A planar transformer having a flat or thin-film primary coil conductor and a secondary coil conductor laminated on the primary coil conductor,
a non-magnetic insulating layer between the primary coil conductor and the secondary coil conductor;
a first non-magnetic insulator in the center of the plane of the primary coil conductor opposite to the non-magnetic insulating layer;
a second non-magnetic insulator in the center of the surface of the secondary coil conductor opposite to the non-magnetic insulating layer;
further comprising a magnetic body covering the non-magnetic insulating layer, the primary coil conductor, the secondary coil conductor, the first non-magnetic insulator, and the second non-magnetic insulator;
At both ends and both side surfaces of the first non-magnetic insulator side surface of the primary coil conductor and at both end portions and both side surfaces of the second non-magnetic insulator side surface of the secondary coil conductor, the magnetic material contacts said primary coil conductor and said secondary coil conductor and covers said primary coil conductor and said secondary coil conductor. The thickness of the first non-magnetic insulator in the direction perpendicular to the plane of the primary coil conductor is 0.8 times or more the width of the primary coil conductor, and the secondary coil conductor of the second non-magnetic insulator is 2. The planar transformer according to claim 1, wherein the thickness of the coil conductor in the direction perpendicular to the plane thereof is 0.8 times or more the width of the secondary coil conductor. The width of the first non-magnetic insulator is 0.6 to 0.8 times the width of the primary coil conductor, and the width of the second non-magnetic insulator is 0.00 of the width of the secondary coil conductor. A planar transformer according to claim 1, characterized in that it is 6 to 0.8 times. 2. The planar transformer according to claim 1, wherein said non-magnetic insulating layer, said first non-magnetic insulator and said second non-magnetic insulator are composed of air.

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