JP3557203B2 - Planar magnetic element - Google Patents

Description

【００２２】
ここで、Ｒｃ（０）はコイルの直流抵抗、ｔｃはコイル導体１０の厚さ、ｄはコイル導体１０のライン幅、ρはコイル導体１０の材料の抵抗率、ｌｋはｋ番目のコイル導体１０の長さである。
【００２３】
しかして、上述した（１）式に基づいて計算したコイル抵抗Ｒｃ（ｆ）の周波数ｆの上昇に伴う増加を考慮した曲線は、図２９中の計算値ａに示すようになり、上述した図１５で述べた実際の平面型インダクタについて測定した等価直列抵抗Ｒの測定値ｂと極めて類似した傾向を呈している。
【００２４】
この場合、図２９において、計算値ａと測定値ｂの間の斜線で示す部分は、軟磁性体の高周波損失による増加分であり、これはコイル抵抗増加分に比べて遥かに小さい。このことから、このような平面コイルを軟磁性体で挟持するような構成の平面型磁気素子における高周波損失の大部分はコイル導体での損失が占め、これがＱ値向上の阻害要因になっていると結論づけることができる。
【００２５】
なお、上述では、平面型磁気素子として平面型インダクタについて述べたが、平面型トランスについても同様で、高周波帯域でのコイル導体の抵抗増加による高周波損失により運転効率の低下を招く原因になっている。
【００２６】
本発明は、上記事情に鑑みてなされたもので、コイル導体に発生する高周波損失を抑制することができる平面型磁気素子を提供することを目的とする。
【００２７】
【課題を解決するための手段】
請求項１記載の発明は、１つ以上の平面コイルを絶縁体を介して磁性体により挟持した平面型磁気素子において、前記平面コイルの外部回路接続用のパッド部に対応する前記軟磁性体の部分に、それぞれ穴部を形成するようにしている。
【００２８】
請求項２記載の発明は、１つ以上の平面コイルを絶縁体を介して磁性体により挟持した平面型磁気素子において、前記平面コイルの外部回路接続用のパッド部にその周縁から複数の切り込みを入れて分割領域を形成するようにしている。
【００２９】
この結果、請求項１記載の発明によれば、磁性体に、それぞれ形成されたパッド部に対応する穴部により、平面コイルのパッド部を貫通する磁性体間の渡り磁束を無くすことができ、パッド部の渡り磁束によるうず電流の発生を抑制でき、かかるうず電流による電力損失の低減を実現できる。
【００３０】
請求項２記載の発明によれば、パッド部自身に多数の切り込みを入れて形成された複数の分割領域により、渡り磁束によるうず電流を各分割領域ごとに細分化することができ、パッド部全体から見たときのうず電流損を小さくすることができる。
【００３１】
【発明の実施の形態】
以下、本発明の実施の形態を図面に従い説明する。
【００３２】
先ず、品質係数Ｑ値を向上させるための例について説明する。
【００３３】
（第１の例）
図１（ａ）（ｂ）（ｃ）は、第１の例に適用される平面型インダクタの概略構成を示している。図において、１１は平面コイルで、この平面コイル１１は、同図（ｃ）に示すように同コイル１１を複数本（図示例では３本（Ｎ＝３））の導体ライン１１ａ、１１ｂ、１１ｃからなるコイル導体１１１で構成し、このコイル導体１１１を同図（ｂ）に示すように正方形のうず巻きパターンに形成している。そして、このような平面コイル１１を同図（ａ）に示すように絶縁体１２を介して軟磁性体１３により挟持するようにしている。
【００３４】
しかして、このような平面型インダクタによれば、平面コイル１１のコイル導体１１１を３分割して３本の導体ライン１１ａ、１１ｂ、１１ｃにより構成していて、これら導体ライン１１ａ、１１ｂ、１１ｃのそれぞれの幅寸法を極めて小さくしているので、各導体ライン１１ａ、１１ｂ、１１ｃでは、垂直交番磁束によって発生するうず電流を抑制することができ、さらに、このうず電流と外部電源から流れ込む強制電流との重畳による高周波電流の電流密度の分布の偏りも小さくできるので、高周波電流は、それぞれの導体ライン１１ａ、１１ｂ、１１ｃ中をほぼ均一に流れるようになり、高周波帯域でのコイル導体１１の抵抗増加を抑えることができ、これにより高周波損失を低減できることになる。
【００３５】
つまり、平面コイル１１のコイル導体１１１をＮ（＝３）分割した場合の周波数ｆにおけるコイル抵抗Ｒｃ（ｆ）は、次式により与えられる。
【００３６】
【数２】

【００３７】
これにより、コイル抵抗Ｒｃ（ｆ）の交流増加分は、Ｎ（＝３）分割された導体ライン１１ａ、１１ｂ、１１ｃによって、分割しない場合の１／Ｎ^２ に抑制できることが確認された。
【００３８】
また、各導体ライン１１ａ、１１ｂ、１１ｃで、垂直交番磁束によって発生するうず電流を抑制できることは、かかるうず電流は、垂直交番磁束を妨げるように発生するものであるから、垂直交番磁束を安定して発生できることにもなり、このことからインダクタンスＬへの影響もなくすことができる。
【００３９】
従って、このように構成した平面型インダクタの周波数特性は、図２に示すように、周波数ｆ（Ｈｚ）がＭＨｚ帯になっても、インダクタンスＬは、ほとんど一定で、しかも等価直列抵抗Ｒの増大も抑えられ、高周波損失の低減が顕著であり、品質係数Ｑの最大値も１０を越え１２にも達することも確認できた。
【００４０】
なお、上述では、正方形うず巻き型の平面コイル１１を絶縁体１２を介して軟磁性体１２で挟持した平面型インダクタについて述べたが、平面コイル１１のパターン形状としては、図３（ａ）（ｂ）（ｃ）および図４（ａ）（ｂ）に示すように、うず巻き型パターンの場合は、円形、正方形、楕円形、長方形などのいずれでもよいとともに、つづら折れの平面コイルパターンとしてもよい。また、これらに用いられる軟磁性体１３としての材料の制限も全く、例えばフェライト系、金属系いずれでも同様の効果が期待できる。
【００４１】
（第２の例）
上述では、平面型磁気素子として平面型インダクタについて述べたが、例えば、図５に示すように構成した平面型トランスについても同様にして適用できる。
【００４２】
この場合も、平面コイル１５を、複数本（ここでも３本）の導体ライン１５ａ、１５ｂ、１５ｃからなるコイル導体１５１により構成し、このような平面コイル１５を２個用いて、これら平面コイル１５を積層するとともに、絶縁体１６を介して軟磁性体１７により挟持するようにしている。この場合、各平面コイル１５、１５に対する磁束１８は図示矢印方向に透過される。
【００４３】
従って、このように構成した平面型トランスについても、上述した平面型インダクタと同様に高周波帯域でのコイル導体１５１の高周波損失を抑えることができるので、従来７０％程度であった運転効率を９０％程度までも高めることができた。
【００４４】
（第３の例）
図６（ａ）（ｂ）は、第３の例の概略構成を示すもので、正方形うず巻きパターンの平面コイル２１を絶縁体２２を介して一軸性の磁気異方性を有する軟磁性体２３により挟持している。
【００４５】
ところで、このような一軸性の磁気異方性を有す軟磁性体２３は、磁化困難軸と磁化容易軸を有するが、これら磁化困難軸と磁化容易軸での励磁に対する軟磁性体の透磁率μは、図８に示すように周波数ｆに対し磁化困難軸励磁領域では、図中ａに示すようにほぼ一定であるのに対して、磁化容易軸励磁領域は、図中ｂに示すように周波数の上昇とともに低下し、高周波領域では、磁束分布は空心の場合のそれに近くなって、空心コイルに極めて近い特性になってしまうことが知られている。
【００４６】
そこで、上述の正方形うず巻きパターンの平面コイル２１では、高周波領域で一定の透磁率μを呈する磁化困難軸励磁領域に対応するコイル導体２１１については、図７（ａ）に示すように３本の導体ライン２１１ａ、２１１ｂ、２１１ｃにより構成し、残りの磁化容易軸励磁領域に対応するコイル導体２１２については、図７（ｂ）（ｃ）（ｄ）に示すように分割しないか、もしくは分割した導体ライン２１２ａ、２１２ｂ、２１２ｃ相互を部分的に短絡するようにしている。つまり、磁化困難軸励磁に対応する領域では、高周波領域で一定の透磁率μを呈することから、図７（ａ）に示すようにコイル導体２１１を導体ライン２１１ａ、２１１ｂ、２１１ｃに分割して、高周波帯域での抵抗増加を抑え、高周波損失を低減できるようにし、残りの磁化容易軸励磁に対応する領域では、透磁率μが小さく空心コイルに極めて近い状態になっていて、垂直磁束による影響が少ないので、図７（ｂ）（ｃ）（ｄ）に示すように、分割しないか、あるいは分割して部分的に短絡するように構成している。
【００４７】
従って、このようにすれば、磁化困難軸励磁に対応する領域では、コイル導体２１１を導体ライン２１１ａ、２１１ｂ、２１１ｃに分割しているので、高周波帯域での抵抗増加を抑え、高周波損失を低減できることで、品質係数Ｑの最大値を高めることができる。また、磁化容易軸励磁に対応する領域では、コイル導体２１２を分割しないか、もしくは分割した導体ライン２１２ａ、２１２ｂ、２１２ｃ相互を部分的に短絡するようにしているが、この部分は、透磁率μが小さく空心コイルに極めて近い状態になっていて垂直磁束による影響が少ないので、抵抗増加による影響を回避できる。
【００４８】
そして、この領域のコイル導体２１２を分割しないか、あるいは分割して部分的に短絡することは、コイル導体が分割された個々の導体ラインの幅は当然のことながら狭くなり、これらの制作をフォトリソグラフィなどによって行うと、導体の幅が細くなるほど、工程中のゴミ等によって導体の断線を起こし易くなるが、このような一部切断に対して抵抗増加の影響の少ない磁化容易軸領域でコイル導体２１２部分の、全てあるいは部分的に電気的に接続されていれば、平面コイル全体の断線を避けることができ、コイル作製の歩留りの向上が期待され、コストの低減も実現できる。
【００４９】
図９（ａ）（ｂ）（ｃ）は、磁化困難軸励磁に対応する領域のコイル導体２１１を導体ライン２１１ａ、２１１ｂ、２１１ｃに分割し、磁化容易軸励磁に対応する領域のコイル導体２１２を分割しないか、もしくは分割した導体ライン２１２ａ、２１２ｂ、２１２ｃ相互を部分的に短絡した場合のコイル導体２１１の導体ライン２１１ａ、２１１ｂ、２１１ｃで断線を生じた場合の例を示すもので、同図（ａ）では、コイル導体２１１の各導体ライン２１１ａ、２１１ｂ、２１１ｃで断線Ａが生じてもコイル導体２１２部分を分割していないので、この時の電気的な接続断は、該当する導体ライン２１１ａ、２１１ｂ、２１１ｃのみに止めることができる。同様にして同図（ｂ）（ｃ）では、コイル導体２１１の各導体ライン２１１ａ、２１１ｂ、２１１ｃで断線Ａが生じてもコイル導体２１２の分割した導体ライン２１２ａ、２１２ｂ、２１２ｃ相互を部分的に短絡しているので、この場合も、電気的な接続断は、該当する導体ライン２１１ａ、２１１ｂ、２１１ｃのみに止めることができるようになり、平面コイル全体の断線を避けることができるようになる。
【００５０】
なお、上述では、正方形うず巻きパターンの平面コイル２１を絶縁体２２を介して一軸性の磁気異方性を有する軟磁性体２３で挟持した平面型インダクタについて述べたが、平面コイル２１のパターン形状としては、図１０（ａ）（ｂ）に示すように楕円形うず巻き型の平面コイル３１を絶縁体３２を介して一軸性の磁気異方性を有する軟磁性体３３で挟持したもの、図１１（ａ）（ｂ）に示すように長方形うず巻き型の平面コイル４１を絶縁体４２を介して一軸性の磁気異方性を有する軟磁性体４３で挟持したもの、図１２（ａ）（ｂ）に示すようにつづれ折れ型の平面コイル５１を絶縁体５２を介して一軸性の磁気異方性を有する軟磁性体５３で挟持したものも考えられる。
【００５１】
この場合、図１０（ａ）（ｂ）に示す楕円形うず巻き型の平面コイル３１を絶縁体３２を介して一軸性の磁気異方性を有する軟磁性体３３で挟持した構成のものでは、長径方向に沿ったコイル導体３１１を磁化困難軸励磁領域に対応させるとともに、複数に分割し、短径方向に沿ったコイル導体３１２を磁化容易軸励磁領域に対応させるとともに、分割しないか、もしくは分割して部分的に短絡するようにようにする。このようにすれば、磁化困難軸励磁領域に平面コイル３１の大部分を占めるコイル導体３１１を対応させることができるので、コイルとして効率のよい動作を期待できる。
【００５２】
また、図１１（ａ）（ｂ）に示す長方形うず巻き型の平面コイル４１を絶縁体４２を介して一軸性の磁気異方性を有する軟磁性体４３で挟持したものについても、長手方向に沿ったコイル導体４１１を磁化困難軸励磁領域に対応させるとともに、複数に分割し、短手方向に沿ったコイル導体４１２を磁化容易軸励磁領域に対応させるとともに、分割しないか、もしくは分割して部分的に短絡するようにようにする。このようにしても図１０の場合と同様な効果を期待できる。
【００５３】
さらに、図１２（ａ）（ｂ）に示すようにつづれ折れ型の平面コイル５１を絶縁体５２を介して一軸性の磁気異方性を有する軟磁性体５３で挟持したものでは、直線部分のコイル導体５１１を磁化困難軸励磁領域に対応させるとともに、複数に分割し、折り曲がり部分のコイル導体５１２を磁化容易軸励磁領域に対応させるとともに、分割しないか、もしくは分割して部分的に短絡するようにようにする。このようにしても図１０の場合と同様な効果を期待できる。
【００５４】
さらにまた、上述では、１個の平面コイルにより平面型インダクタを構成したものについてのべたが、図１３（ａ）（ｂ）に示すように、うず巻きパターン平面コイル６１、６２を同一平面上に隣接して配置するとともに、これら平面コイル６１、６２間を電気的に直列接続したものを絶縁体６３を介して一軸性の磁気異方性を有する軟磁性体６４で挟持するようにしたものにも適用できる。この場合も長手方向に沿ったコイル導体６１１、６２１を磁化困難軸励磁領域に対応させるとともに、複数に分割し、短手方向に沿ったコイル導体６１２、６２２を磁化容易軸励磁領域に対応させるとともに、分割しないか、もしくは分割して部分的に短絡するようにようにする。このようにしても図１０の場合と同様な効果を期待でき、さらに大きなインダクタンス値を有する平面型インダクタを実現できる。また、上述では、うず巻きパターン平面コイルの外形形状が矩形状または楕円状である時に、一軸性の磁気異方性を有する軟磁性体を用いる場合について述べたが、うず巻きパターン平面コイルの外形形状が円形の場合には、軟磁性体として磁気特性が等方性のものを用いるのがよい。
【００５５】
（第１の実施の形態）
ところで、上述した平面コイルを軟磁性体で挟み込むような平面型の磁気素子においては、上下方向に位置する軟磁性体からの渡り磁束は、コイル導体の交流抵抗増加の原因になるばかりが、外部回路との接続のために設けられるパッド部にも損失を発生させることがある。
【００５６】
図１４は、このような外部回路接続用のパッド部を設けた従来の平面型インダクタの一例を示すもので、平面コイル７１を絶縁体７２を介して上部軟磁性体７３１、下部軟磁性体７３２により挟持している。この場合、上部軟磁性体７３１は、平面コイル７１に穴部７３１ａを形成し、この穴部７３１ａに外部回路接続のためのボンディングワイヤ接続用のパッド部７４を配置している。
【００５７】
そして、このようにした平面型インダクタでは、平面コイル７１より発生した磁束φの流れは、図１４の図示矢印方向になっている。
【００５８】
この場合、下部磁性体７３２は、パッド部７４に対応する穴部を有していない。このため、パッド部７４付近での上部軟磁性体７３１と下部磁性体７３２の間の渡り磁束φＡ は、下部磁性体７３２の磁束の吸い込みのためパッド部７４の全面を貫通するようになる。この結果、図１５に示すようにパッド部７４面を貫通する磁束φＡ によりパッド部７４の導体内に図示方向のうず電流ｉが発生し、このうず電流ｉが電力損失となって、素子全体の交流抵抗増加の大きな要因となるという問題があった。
【００５９】
そこで、この第１の実施の形態では、パッド部でのうず電流発生を抑制して、素子全体の交流抵抗の増加を阻止するようにしている。
【００６０】
図１６は、第１の実施の形態の概略構成を示すもので、図１４と同一部分には同符号を付している。
【００６１】
この場合、平面コイル７１を上部軟磁性体７３１とともに挟持する下部磁性体７３２は、平面コイル７１のパッド部７４に対応する穴部７３２ａを形成している。この穴部７３２ａは、上部軟磁性体７３１の穴部７３１ａとともにパッド部７４の外形寸法より十分に大きな寸法にしている。
【００６２】
しかして、このような構成とすると、下部軟磁性体７３２にも、パッド部７４の外形寸法より十分に大きな寸法の穴部７３２ａを形成して、穴部７３２ａの位置に相当していた従来の下部軟磁性体７３２での磁束の吸い込みを無くすようにしたので、パッド部７４付近での上部軟磁性体７３１と下部磁性体７３２間の渡り磁束φＡ のうちでパッド部７４面を貫通するものをほとんど無くすことが可能となり、かかる渡り磁束φＡ によるうず電流の発生を抑制できることになる。
【００６３】
従って、このようにすれば、平面コイル７１を挟持する上部軟磁性体７３１、下部軟磁性体磁性体７３２のそれぞれ平面コイル７１のパッド部７４に対応する部分にパッド部７４の外形寸法より十分に大きな寸法の穴部７３１ａ、７３２ａを形成して、平面コイル７１のパッド部７４を貫通する上部軟磁性体７３１と下部磁性体７３２間の渡り磁束φＡ を無くすようにしたので、パッド部７４での渡り磁束φＡ によるうず電流の発生を抑制することができ、かかるうず電流による電力損失の低減と、素子の交流抵抗の増加が抑制され、素子の高効率化を実現することができる。
【００６４】
なお、上述では、平面コイル７１を挟持する上部軟磁性体７３１、下部軟磁性体磁性体７３２のそれぞれ平面コイル７１のパッド部７４に対応する部分にパッド部７４の外形寸法より十分に大きな寸法の穴部７３１ａ、７３２ａを形成するようにしたが、例えば、図１６と同一部分には同符号を付した図１７に示すように上部軟磁性体７３１の穴部７３１ａと下部軟磁性体磁性体７３２の穴部７３２ａとの間を筒状の磁性体７３３で接続するようにしてもよい。
【００６５】
このようにすれば、上部軟磁性体７３１と下部軟磁性体磁性体７３２の間の磁束φは、全て筒状の磁性体７３３を通るようになるので、パッド部７４を貫通する磁束を皆無にでき、パッド部７４でのうず電流発生をさらに確実に抑制することが可能となり、上述に増して、電力損失の低減と、素子の交流抵抗の増加が抑制され、素子の高効率化が実現できる。
【００６６】
（第２の実施の形態）
第１の実施の形態では、パッド部を貫通する磁束を無くすことで、パッド部に発生するうず電流を抑制するようにしたが、この第２実施の形態では、パッド部自身での工夫によりうず電流による影響を低減するようにしている。
【００６７】
この場合、図１８に示すように、パッド部８１自身に多数の切り込み８２を入れるようにしている。
【００６８】
この切り込み８２の入れ方は多様であり限定されないが、図１８では、矩形状のパッド部８１の中心部を除いて、この周縁から中心部に向かう複数の切り込み８２を入れて複数の分割領域８１１を形成している。この場合、切り込み８２により分割された複数の分割領域８１１は、中心部で電気的に接続されている。
【００６９】
なお、図面中、８３は軟磁性体、８３１は軟磁性体８３に形成された穴部を示している。これら軟磁性体８３、穴部８３１の詳細構成は、第１の実施の形態で述べたと同様であり、ここでの説明は省略する。
【００７０】
しかして、このような構成とすると、いま、パッド部８１の中心部に渡り磁束φＡ が貫通し、この渡り磁束φＡ によりうず電流が生じると、この時のうず電流ループは、各分割領域８１１ごとに微細なうず電流ｉＡａに細分化され発生されるようになる。これにより、パッド部８１全体から見た時のうず電流損を小さくすることが可能となり、このようにしても、電力損失の低減と、素子の交流抵抗の増加が抑制され、素子の高効率化を実現できる。
【００７１】
【発明の効果】
以上述べたように、本発明によれば、平面コイルを挟持する一対の軟磁性体に、それぞれパッド部の外形寸法より十分に大きな寸法の穴部を形成して、平面コイル中空部に位置されるパッド部を貫通する軟磁性体間の渡り磁束を無くすようにしたので、パッド部の渡り磁束によるうず電流の発生を抑制でき、うず電流による電力損失の低減と、素子の交流抵抗の増加が抑制され、素子の高効率化を実現できる。
【００７２】
さらにまた、パッド部自身に多数の切り込みを入れて複数の分割領域を形成し渡り磁束によりうず電流を各分割領域ごとに微細なうず電流に細分化することで、パッド部全体から見た時のうず電流損を小さくするようにしたので、これによっても、電力損失の低減と、素子の交流抵抗の増加が抑制され、素子の高効率化を実現できる。
【図面の簡単な説明】
【図１】品質係数Ｑ値を向上させるための第１の例の平面型インダクタの概略構成を示す図。
【図２】第１の例の平面型インダクタの周波数特性を示す図。
【図３】第１の例の平面型インダクタに用いられる平面コイルのパターン形状を示す図。
【図４】第１の例の平面型インダクタに用いられる平面コイルのパターン形状を示す図。
【図５】第２の例の平面型トランスの概略構成を示す図。
【図６】第３の例の平面型インダクタの概略構成を示す図。
【図７】第３の例に用いられるコイル導体の構成を示す図。
【図８】第３の例に用いられる軟磁性体の磁化困難軸励磁と磁化容易軸励磁による透磁率の変化を示す図。
【図９】第３の例に用いられるコイル導体に断線を生じた場合の例を示す図。
【図１０】第３の例の楕円形うず巻き型の平面コイルを用いた平面型インダクタの概略構成を示す図。
【図１１】第３の例の長方形うず巻き型の平面コイルを用いた平面型インダクタの概略構成を示す図。
【図１２】第３の例のつづれ折れ型の平面コイルを用いた平面型インダクタの概略構成を示す図。
【図１３】第３の例の２個の平面コイルを用いた平面型インダクタの概略構成を示す図。
【図１４】本発明の第１の実施の形態の説明に用いる従来の平面型インダクタの概略構成を示す図。
【図１５】第１の実施の形態の説明に用いるパッド部でのうず電流の発生状態を示す図。
【図１６】第１の実施の形態の平面型インダクタの概略構成を示す図。
【図１７】第１の実施の形態の他の平面型インダクタの概略構成を示す図。
【図１８】本発明の第２の実施の形態の平面型インダクタに用いられるパッド部の概略構成を示す図。
【図１９】従来の平面型インダクタの一例を示す図。
【図２０】従来の平面型インダクタの周波数特性を示す図。
【図２１】従来の平面型インダクタの他例を示す図。
【図２２】従来の平面型インダクタの周波数特性を示す図。
【図２３】従来のうず巻きコイルパターンの平面型インダクタの素子内磁束分布の一例を示す図。
【図２４】従来のつづら折れコイルパターンの平面型インダクタの素子内磁束分布の一例を示す図。
【図２５】軟磁性体の面内磁束成分により発生するうず電流を説明するための図。
【図２６】軟磁性体の垂直磁束成分により発生するうず電流を説明するための図。
【図２７】垂直磁束成分により発生するコイル導体中のうず電流を説明するための図。
【図２８】コイル導体中の高周波電流密度の分布を説明するための図。
【図２９】従来の平面型インダクタについて測定したコイル抵抗の測定値と計算値の関係を示す図。
【符号の説明】
１１、２１、３１、４１、５１…平面コイル、
１１１、２１１、２１２、３１１、３１２、４１１、４１２、５１１、５１２…コイル導体、
１１ａ、１１ｂ、１１ｃ、２１１ａ、２１１ｂ、２１１ｃ、２１２ａ、２１２ｂ、２１２ｃ…導体ライン、
１２…絶縁体、
１３、２２、３２、４２、５２、…軟磁性体。
７１…平面コイル、
７１１…中空部、
７２…平面コイル、
７３１、７３２、８３…軟磁性体、
７３１ａ、７３２ａ、８３１…穴部、
７４、８１…パッド部、
８１１…分割領域、
８２…切り込み、[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a planar magnetic element used for various high-frequency components such as a choke coil for a switching power supply and a transformer.
[0002]
[Prior art]
Recently, with the advent of the multimedia age, various portable electronic devices have been improved in the degree of integration of electronic circuits by LSI technology, the progress of component mounting technology, and the emergence of high-energy batteries such as lithium batteries and nickel-metal hydride batteries Together with this, electronic devices are being enhanced in function, reduced in size, reduced in thickness, and reduced in weight.
[0003]
By the way, a switching power supply is used as a stabilizing power supply unit in a power supply unit of such an electronic device. However, it is difficult to reduce the size and weight of such a switching power supply while maintaining high power conversion efficiency. In terms of size, weight, and cost, the proportion of such equipment in the overall equipment is steadily increasing.
[0004]
Therefore, as a countermeasure against this, it is conceivable to increase the switching frequency of the power supply and use small power supply components such as inductors, transformers, and capacitors, thereby realizing a reduction in size and weight. On the other hand, the power conversion efficiency of the components decreases because the loss increases as the frequency increases. For high frequency power conversion, therefore, it is essential to reduce the loss of these components.Furthermore, it is difficult to reduce the height of magnetic components such as inductors and transformers. It is also the cause.
[0005]
In view of this, a flat inductor and a transformer using a flat coil and a soft magnetic film have been proposed to realize an ultra-compact and thin power supply.
[0006]
FIGS. 19 (a) and 19 (b) show an example of a conventional planar inductor. A square spiral type planar coil 1 as shown in FIG. 19 (b) is an insulator as shown in FIG. 19 (a). The soft magnetic members 3 are sandwiched between the members 2.
[0007]
However, the frequency characteristics of the planar inductor configured as described above are as shown in FIG. 20. When the frequency f (Hz) increases, the inductance L is almost constant, whereas the coil resistance R sharply increases. The quality factor Q remains at a low value of less than 10. In general, in the case of an inductance element, the quality factor Q value exceeds 10 and it is considered that the higher the quality factor, the better. Therefore, a large improvement in the Q value is required.
[0008]
In this case, it is considered that a factor such as a high-frequency loss (eddy current loss, hysteresis loss) in the soft magnetic body 3 and a high-frequency loss of the coil 1 are factors that hinder the improvement of the Q value.
[0009]
Therefore, as another example of a planar inductor, as shown in FIG. 21, an elliptical spiral pattern is conventionally used for the planar coil 4 and the planar coil 4 is provided with an uniaxial magnetic anisotropy via an insulating film. A material sandwiched by a soft magnetic material 5 having a hard magnetization axis has also been considered. When the soft magnetic material 5 having such uniaxial magnetic anisotropy is used, the soft magnetic material 5 utilizes the rotation mode of magnetization, so that the eddy current loss generated in the soft magnetic material 5 can be reduced, and It can be expected that the high-frequency loss in the body 5 can be reduced.
[0010]
However, the frequency characteristic of such a planar inductor is as shown in FIG. 22, and the maximum value of the quality factor Q never exceeded 10.
[0011]
[Problems to be solved by the invention]
Thus, the present applicant has analyzed the high-frequency loss of the planar inductor with respect to the planar magnetic element in which the planar coil is sandwiched by the soft magnetic material via the insulator, and found the following.
[0012]
(A). For example, as shown in FIG. 23 (a), in the case where the planar coil 6 of the spiral pattern is sandwiched between the soft magnetic bodies 8 via the insulator 7, the internal magnetic flux is generated in the plane of the soft magnetic body 8. There is a magnetic flux component Bi and a vertical magnetic flux component Bg, and the magnetic flux distribution of the in-plane magnetic flux component Bi and the vertical magnetic flux component Bg is as shown in FIG.
[0013]
Similarly, as shown in FIG. 24 (a), even when a planar coil 9 having a serpentine pattern is sandwiched by a soft magnetic body 8 via an insulator 7, the internal magnetic flux of the soft magnetic body 8 The in-plane magnetic flux component Bi and the vertical magnetic flux component Bg exist, and the magnetic flux distribution of the in-plane magnetic flux component Bi and the vertical magnetic flux component Bg is as shown in FIG.
[0014]
(B). Then, the in-plane magnetic flux component Bi passing through the soft magnetic body 8 generates an eddy current jm, p flowing in the thickness direction of the soft magnetic body 8 as shown in FIG.
[0015]
(C). Similarly, the vertical magnetic flux component Bg passing through the soft magnetic material 8 generates an eddy current jm, i in the plane of the soft magnetic material 8 as shown in FIG.
[0016]
(D). Among them, the vertical magnetic flux component Bg passing through the k-th coil conductor 10 constituting the plane coil 6 (9) is generated along the longitudinal direction of the coil conductor 10 along the longitudinal direction of the coil conductor 10 as shown in FIG. 1 is generated. In this case, in the planar coil 6 having the spiral pattern, since the direction of the magnetic flux due to the vertical magnetic flux component Bg is the same at any position in the width direction of the coil conductor 10, the current of the high-frequency current flowing through the coil conductor 10 as shown in FIG. The distribution of the density is higher at one end and lower at the other end with respect to the center of the coil conductor 10, and the non-uniformity of the current density becomes remarkable.
[0017]
This means that in the high-frequency band, the high-frequency current flowing through the coil conductor 10 does not uniformly flow through the coil conductor 10 but flows only at one end, so that the resistance value at the coil conductor 10 sharply increases. This accounts for a considerable proportion of the high-frequency loss, and is considered to be a hindrance to the improvement of the Q value.
[0018]
Further, when the increase in the high-frequency resistance in the planar coil due to the vertical magnetic flux component Bg was examined, the following was also found.
[0019]
FIG. 27 focuses on the k-th coil conductor 10 constituting the planar coil 6 (9), and the vertical magnetic flux goes from bottom to top, and this direction does not change in the section where the k-th conductor 10 exists. . Note that Bgk (x) in FIG. 27 represents the vertical magnetic flux density passing through the k-th coil conductor 10.
[0020]
The current density in the coil conductor 10 is superimposed on the forced current I flowing from the external power supply and the eddy current jc, l generated by the vertical alternating magnetic flux. As shown in FIG. 28, the current density is high at the left end of the coil conductor 10 and low at the right end. In this case, the magnetic flux density Bgk (x) passing through the coil conductor 10 is constant in the section where the coil conductor 10 exists. Assuming Bgk, the coil resistance Rc (f) at the frequency f is given by the following equation.
[0021]
(Equation 1)

[0022]
Here, Rc (0) is the DC resistance of the coil, tc is the thickness of the coil conductor 10, d is the line width of the coil conductor 10, ρ is the resistivity of the material of the coil conductor 10, and lk is the k-th coil conductor 10. Is the length of
[0023]
Thus, a curve in consideration of the increase in the coil resistance Rc (f) with the increase in the frequency f calculated based on the above equation (1) is as shown by the calculated value a in FIG. It shows a tendency very similar to the measured value b of the equivalent series resistance R measured for the actual planar inductor described in FIG.
[0024]
In this case, in FIG. 29, the hatched portion between the calculated value a and the measured value b is the increase due to the high-frequency loss of the soft magnetic material, which is much smaller than the increase in the coil resistance. For this reason, most of the high-frequency loss in the planar magnetic element having such a configuration in which such a planar coil is sandwiched by soft magnetic materials is occupied by the loss in the coil conductor, and this is a hindrance factor for improving the Q value. It can be concluded.
[0025]
In the above description, a planar inductor has been described as a planar magnetic element. However, the same applies to a planar transformer, which causes a decrease in operating efficiency due to a high-frequency loss due to an increase in resistance of a coil conductor in a high-frequency band. .
[0026]
The present invention has been made in view of the above circumstances, and has as its object to provide a planar magnetic element that can suppress high-frequency loss generated in a coil conductor.
[0027]
[Means for Solving the Problems]
The invention according to claim 1 is a planar magnetic element in which one or more planar coils are sandwiched by a magnetic body via an insulator, wherein the soft magnetic body corresponding to a pad portion for connecting an external circuit of the planar coil is provided. A hole is formed in each part.
[0028]
According to a second aspect of the present invention, in the planar magnetic element in which one or more planar coils are sandwiched by a magnetic body via an insulator, a plurality of cuts are formed in a pad portion for connecting an external circuit of the planar coil from a peripheral edge thereof. To form a divided area.
[0029]
As a result, according to the first aspect of the present invention, it is possible to eliminate the crossover magnetic flux between the magnetic materials penetrating the pad portion of the planar coil by the holes corresponding to the pad portions formed on the magnetic material, The generation of the eddy current due to the crossover magnetic flux of the pad portion can be suppressed, and the power loss due to the eddy current can be reduced.
[0030]
According to the second aspect of the present invention, the eddy current due to the crossover magnetic flux can be subdivided for each divided region by the plurality of divided regions formed by making a large number of cuts in the pad portion, and the entire pad portion can be divided. The eddy current loss when viewed from above can be reduced.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0032]
First, an example for improving the quality factor Q value will be described.
[0033]
(First example)
FIGS. 1A, 1B, and 1C show a schematic configuration of a planar inductor applied to the first example. In the figure, reference numeral 11 denotes a planar coil, and the planar coil 11 has a plurality of (three (N = 3) in the illustrated example) conductor lines 11a, 11b, 11c as shown in FIG. , And the coil conductor 111 is formed in a square spiral pattern as shown in FIG. Then, such a planar coil 11 is sandwiched by a soft magnetic body 13 via an insulator 12 as shown in FIG.
[0034]
Thus, according to such a planar inductor, the coil conductor 111 of the planar coil 11 is divided into three to be constituted by three conductor lines 11a, 11b, 11c. Since the respective width dimensions are extremely small, the eddy current generated by the vertical alternating magnetic flux can be suppressed in each of the conductor lines 11a, 11b, and 11c, and furthermore, the eddy current and the forced current flowing from the external power supply are reduced. Of the current density distribution of the high-frequency current due to the superposition of the high-frequency current can be reduced, so that the high-frequency current flows almost uniformly in each of the conductor lines 11a, 11b, and 11c, and the resistance of the coil conductor 11 in the high-frequency band increases. , And high frequency loss can be reduced.
[0035]
That is, the coil resistance Rc (f) at the frequency f when the coil conductor 111 of the planar coil 11 is divided into N (= 3) is given by the following equation.
[0036]
(Equation 2)

[0037]
As a result, the AC increase of the coil resistance Rc (f) is reduced by N (= 3) by the conductor lines 11a, 11b, and 11c, which are 1 / N of the case where no division is performed. ² It was confirmed that it could be suppressed.
[0038]
In addition, since the eddy current generated by the vertical alternating magnetic flux can be suppressed in each of the conductor lines 11a, 11b, and 11c, since the eddy current is generated so as to hinder the vertical alternating magnetic flux, the vertical alternating magnetic flux is stabilized. Therefore, the influence on the inductance L can be eliminated.
[0039]
Therefore, as shown in FIG. 2, the frequency characteristics of the planar inductor thus configured are such that the inductance L is almost constant and the equivalent series resistance R increases even when the frequency f (Hz) is in the MHz band. It was also confirmed that the high frequency loss was remarkably reduced, and that the maximum value of the quality factor Q exceeded 10 and reached 12 as well.
[0040]
In the above description, the planar inductor in which the square spiral planar coil 11 is sandwiched by the soft magnetic material 12 via the insulator 12 has been described. However, the pattern shape of the planar coil 11 is shown in FIGS. As shown in FIGS. 4 (c) and 4 (a) and 4 (b), in the case of the spiral pattern, any of circular, square, elliptical, rectangular and the like may be used, and a meandering planar coil pattern may be used. In addition, the material of the soft magnetic material 13 used in these materials is not limited, and for example, the same effect can be expected in any of ferrite-based and metal-based materials.
[0041]
(Second example)
In the above description, a planar inductor was described as a planar magnetic element. However, for example, a planar transformer configured as shown in FIG. 5 can be similarly applied.
[0042]
Also in this case, the planar coil 15 is constituted by a coil conductor 151 composed of a plurality of (three in this case) conductor lines 15a, 15b, and 15c. And is sandwiched by a soft magnetic body 17 via an insulator 16. In this case, the magnetic flux 18 for each of the planar coils 15, 15 is transmitted in the direction indicated by the arrow.
[0043]
Therefore, also in the planar transformer configured as described above, the high-frequency loss of the coil conductor 151 in the high-frequency band can be suppressed in the same manner as the planar inductor described above. It could be raised to the extent.
[0044]
(Third example)
FIGS. 6A and 6B show a schematic configuration of the third example. A planar coil 21 having a square spiral pattern is formed by a soft magnetic body 23 having uniaxial magnetic anisotropy via an insulator 22. It is pinched.
[0045]
By the way, the soft magnetic material 23 having such uniaxial magnetic anisotropy has a hard axis and an easy axis, but the magnetic permeability of the soft magnetic material with respect to the excitation in the hard axis and the easy axis. μ is almost constant in the hard axis excitation region with respect to the frequency f as shown in FIG. 8 as shown in FIG. 8A, whereas the easy axis excitation region is as shown in FIG. It is known that the magnetic flux distribution decreases as the frequency increases, and in a high-frequency region, the magnetic flux distribution becomes close to that in the case of the air core, and has characteristics very close to those of the air core coil.
[0046]
Therefore, in the planar coil 21 having the square spiral pattern described above, as shown in FIG. 7A, three coil conductors 211 corresponding to the hard axis excitation region exhibiting a constant magnetic permeability μ in the high frequency region are provided. The coil conductors 212 constituted by the lines 211a, 211b, and 211c and corresponding to the remaining easy axis excitation regions are not divided as shown in FIGS. 212a, 212b and 212c are partially short-circuited to each other. That is, in the region corresponding to the hard axis excitation, since the magnetic permeability exhibits a constant permeability μ in the high frequency region, the coil conductor 211 is divided into conductor lines 211a, 211b, and 211c as shown in FIG. The resistance increase in the high-frequency band is suppressed, and the high-frequency loss can be reduced.In the remaining area corresponding to the easy axis excitation, the magnetic permeability μ is small and it is very close to the air-core coil. Since the number is small, as shown in FIGS. 7B, 7C, and 7D, it is configured not to be divided, or to be divided and partially short-circuited.
[0047]
Therefore, in this case, in the region corresponding to the hard axis excitation, the coil conductor 211 is divided into the conductor lines 211a, 211b, and 211c, so that an increase in resistance in a high frequency band can be suppressed, and a high frequency loss can be reduced. Thus, the maximum value of the quality factor Q can be increased. In the region corresponding to the easy axis excitation, the coil conductor 212 is not divided, or the divided conductor lines 212a, 212b, and 212c are partially short-circuited to each other. Is small and very close to the air-core coil, and the influence of the vertical magnetic flux is small, so that the influence of the increase in resistance can be avoided.
[0048]
If the coil conductor 212 in this area is not divided or is divided and short-circuited partially, the width of each conductor line into which the coil conductor is divided naturally becomes narrower. When performed by lithography or the like, as the width of the conductor becomes narrower, the conductor is more likely to be disconnected due to dust or the like during the process. If all or part of the 212 portion is electrically connected, disconnection of the entire planar coil can be avoided, and an improvement in coil production yield is expected, and a reduction in cost can be realized.
[0049]
FIGS. 9A, 9B, and 9C show that the coil conductor 211 in the region corresponding to the hard axis excitation is divided into conductor lines 211a, 211b, and 211c, and the coil conductor 212 in the region corresponding to the easy axis excitation is divided. This figure shows an example in which the conductor lines 212a, 212b, and 212c are not divided or the conductor lines 211a, 211b, and 211c of the coil conductor 211 are disconnected when the conductor lines 212a, 212b, and 212c are partially short-circuited. In a), even if a break A occurs in each of the conductor lines 211a, 211b, 211c of the coil conductor 211, the coil conductor 212 is not divided, so that the electrical disconnection at this time is caused by the corresponding conductor line 211a, It can be limited to only 211b and 211c. Similarly, in FIGS. 9B and 9C, even if a break A occurs in each of the conductor lines 211a, 211b, 211c of the coil conductor 211, the divided conductor lines 212a, 212b, 212c of the coil conductor 212 are partially connected to each other. In this case, the electrical connection can be stopped only at the corresponding conductor lines 211a, 211b, and 211c because of the short-circuit, so that disconnection of the entire planar coil can be avoided.
[0050]
In the above description, a planar inductor in which a planar coil 21 having a square spiral pattern is sandwiched by a soft magnetic substance 23 having uniaxial magnetic anisotropy via an insulator 22 has been described. As shown in FIGS. 10A and 10B, an elliptical spiral wound planar coil 31 is sandwiched by a soft magnetic body 33 having uniaxial magnetic anisotropy via an insulator 32, and FIG. a) As shown in FIGS. 12 (a) and 12 (b), a rectangular spiral coiled planar coil 41 is sandwiched by a soft magnetic body 43 having uniaxial magnetic anisotropy via an insulator 42 as shown in FIGS. As shown in the figure, it is also conceivable that the foldable plane coil 51 is sandwiched by a soft magnetic body 53 having uniaxial magnetic anisotropy via an insulator 52.
[0051]
In this case, in the configuration in which the elliptical spiral wound planar coil 31 shown in FIGS. 10A and 10B is sandwiched by the soft magnetic material 33 having uniaxial magnetic anisotropy via the insulator 32, the long diameter The coil conductor 311 along the direction is made to correspond to the hard axis excitation region and divided into a plurality, and the coil conductor 312 along the minor axis direction is made to correspond to the easy axis excitation region and is not divided or divided. So that it is partially short-circuited. With this configuration, the coil conductor 311 occupying most of the planar coil 31 can be made to correspond to the hard axis excitation region, so that efficient operation as a coil can be expected.
[0052]
11A and 11B, a rectangular coil 41 is sandwiched by a soft magnetic material 43 having uniaxial magnetic anisotropy via an insulator 42. The coil conductor 411 corresponding to the hard axis excitation region is divided into a plurality of portions, and the coil conductor 412 along the lateral direction is corresponded to the easy axis excitation region, and is not divided or is partially divided. So that it is short-circuited. Even in this case, the same effect as in the case of FIG. 10 can be expected.
[0053]
Further, as shown in FIGS. 12A and 12B, in the case where the serpentine planar coil 51 is sandwiched by the soft magnetic body 53 having uniaxial magnetic anisotropy via the insulator 52, The coil conductor 511 is made to correspond to the hard axis excitation region and is divided into a plurality of parts, and the bent portion of the coil conductor 512 is made to correspond to the easy axis excitation region, and is not divided or is divided and partially short-circuited. Like so. Even in this case, the same effect as in the case of FIG. 10 can be expected.
[0054]
Further, in the above description, the planar inductor is constituted by one planar coil. However, as shown in FIGS. 13A and 13B, the spiral-wound pattern planar coils 61 and 62 are adjacent on the same plane. The planar coils 61 and 62 are electrically connected in series, and the planar coils 61 and 62 are sandwiched by a soft magnetic body 64 having uniaxial magnetic anisotropy via an insulator 63. Applicable. In this case as well, the coil conductors 611 and 621 along the longitudinal direction are made to correspond to the hard axis excitation region, and the coil conductors 612 and 622 along the short direction are made to correspond to the easy axis excitation region while being divided into a plurality. In such a case, the circuit is not divided, or is divided so as to be partially short-circuited. Even in this case, the same effect as in the case of FIG. 10 can be expected, and a planar inductor having a larger inductance value can be realized. In the above description, the case where a soft magnetic material having uniaxial magnetic anisotropy is used when the outer shape of the spiral pattern planar coil is rectangular or elliptical has been described. In the case of a circular shape, it is preferable to use a soft magnetic material having isotropic magnetic characteristics.
[0055]
(First Embodiment)
By the way, in a flat type magnetic element in which the above-mentioned planar coil is sandwiched between soft magnetic materials, the crossover magnetic flux from the soft magnetic material located in the vertical direction only causes an increase in the AC resistance of the coil conductor. In some cases, a pad portion provided for connection to a circuit may also generate a loss.
[0056]
FIG. 14 shows an example of a conventional planar inductor provided with such a pad portion for connecting an external circuit. A planar coil 71 is formed by an upper soft magnetic body 731 and a lower soft magnetic body 732 via an insulator 72. It is pinched by. In this case, the upper soft magnetic body 731 has a hole 731a formed in the planar coil 71, and a pad portion 74 for bonding wire connection for connecting an external circuit is arranged in the hole 731a.
[0057]
In such a planar inductor, the flow of the magnetic flux φ generated from the planar coil 71 is in the direction of the arrow shown in FIG.
[0058]
In this case, the lower magnetic body 732 does not have a hole corresponding to the pad 74. For this reason, the crossover magnetic flux φA between the upper soft magnetic body 731 and the lower magnetic body 732 near the pad section 74 penetrates the entire surface of the pad section 74 for absorbing the magnetic flux of the lower magnetic body 732. As a result, as shown in FIG. 15, the magnetic flux φA penetrating through the surface of the pad portion 74 generates an eddy current i in the conductor of the pad portion 74 in the illustrated direction, and this eddy current i becomes a power loss, and There was a problem that it became a major factor of the increase in AC resistance.
[0059]
Thus, in the first embodiment, the generation of eddy current in the pad portion is suppressed, and the increase in the AC resistance of the entire device is prevented.
[0060]
FIG. 16 shows a schematic configuration of the first embodiment, and the same parts as those in FIG. 14 are denoted by the same reference numerals.
[0061]
In this case, the lower magnetic body 732 that sandwiches the planar coil 71 together with the upper soft magnetic body 731 forms a hole 732a corresponding to the pad 74 of the planar coil 71. The hole 732a and the hole 731a of the upper soft magnetic body 731 have a size sufficiently larger than the outer dimensions of the pad 74.
[0062]
With such a configuration, a hole 732a having a size sufficiently larger than the outer dimensions of the pad portion 74 is formed in the lower soft magnetic body 732 to correspond to the position of the hole 732a. Since the suction of the magnetic flux by the lower soft magnetic body 732 is eliminated, the crossing magnetic flux φA between the upper soft magnetic body 731 and the lower magnetic body 732 in the vicinity of the pad part 74 is one that penetrates the surface of the pad part 74. This can be almost eliminated, and the generation of the eddy current due to the cross magnetic flux φA can be suppressed.
[0063]
Accordingly, in this way, the upper soft magnetic body 731 and the lower soft magnetic body 732 sandwiching the planar coil 71 are sufficiently larger than the external dimensions of the pad section 74 at the portions corresponding to the pad sections 74 of the planar coil 71 respectively. Since the large-sized holes 731a and 732a are formed to eliminate the transition magnetic flux φA between the upper soft magnetic member 731 and the lower magnetic member 732 penetrating the pad portion 74 of the planar coil 71, the pad portion 74 has The generation of the eddy current due to the cross magnetic flux φA can be suppressed, the power loss due to the eddy current can be reduced, and the increase in the AC resistance of the element can be suppressed, and the efficiency of the element can be increased.
[0064]
In the above description, each of the upper soft magnetic body 731 and the lower soft magnetic body 732 sandwiching the plane coil 71 has a size sufficiently larger than the outer dimension of the pad section 74 at a portion corresponding to the pad section 74 of the plane coil 71. The holes 731a and 732a are formed. For example, the same portions as those in FIG. 16 are denoted by the same reference numerals, and as shown in FIG. 17, the holes 731a and the lower soft magnetic material 732 of the upper soft magnetic material 731 are provided. The hole 732a may be connected with a cylindrical magnetic body 733.
[0065]
By doing so, the magnetic flux φ between the upper soft magnetic material 731 and the lower soft magnetic material 732 all passes through the cylindrical magnetic material 733, so that no magnetic flux penetrates the pad portion 74. As a result, it is possible to more reliably suppress the generation of eddy current in the pad portion 74, and to reduce the power loss and the increase in the AC resistance of the element more than described above, thereby realizing high efficiency of the element. .
[0066]
(Second embodiment)
In the first embodiment, the eddy current generated in the pad portion is suppressed by eliminating the magnetic flux penetrating the pad portion. However, in the second embodiment, the eddy current is devised by the device of the pad portion itself. The effect of the current is reduced.
[0067]
In this case, as shown in FIG. 18, a large number of cuts 82 are made in the pad portion 81 itself.
[0068]
The cuts 82 may be formed in various ways and are not limited. In FIG. 18, except for the center of the rectangular pad portion 81, a plurality of cuts 82 are formed from the periphery to the center to form a plurality of divided regions 811. Is formed. In this case, the plurality of divided regions 811 divided by the cuts 82 are electrically connected at the center.
[0069]
In the drawings, reference numeral 83 denotes a soft magnetic material, and reference numeral 831 denotes a hole formed in the soft magnetic material 83. The detailed configurations of the soft magnetic body 83 and the hole 831 are the same as those described in the first embodiment, and a description thereof will not be repeated.
[0070]
With such a configuration, when the magnetic flux φA penetrates through the center of the pad portion 81 and an eddy current is generated by the crossed magnetic flux φA, the eddy current loop at this time becomes The eddy current iAa is finely divided and generated. This makes it possible to reduce the eddy current loss when viewed from the entire pad portion 81. Even in this case, the power loss and the increase in the AC resistance of the element are suppressed, and the efficiency of the element is improved. Can be realized.
[0071]
【The invention's effect】
As described above, according to the present invention, a pair of soft magnetic members sandwiching a planar coil are each formed with a hole having a size sufficiently larger than the outer dimensions of the pad portion, and are positioned in the hollow portion of the planar coil. Since the crossover magnetic flux between the soft magnetic materials penetrating the pad section is eliminated, the generation of eddy current due to the crossover magnetic flux of the pad section can be suppressed, reducing the power loss due to the eddy current and increasing the AC resistance of the element. Thus, the efficiency of the device can be increased.
[0072]
Furthermore, a large number of cuts are made in the pad portion itself to form a plurality of divided regions, and the eddy current is subdivided into minute eddy currents for each divided region by the crossover magnetic flux, so that the eddy current when viewed from the entire pad portion is obtained. Since the eddy current loss is reduced, the power loss can be reduced and the increase in the AC resistance of the element can be suppressed, thereby realizing high efficiency of the element.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a planar inductor according to a first example for improving a quality factor Q value;
FIG. 2 is a diagram illustrating frequency characteristics of the planar inductor according to the first example;
FIG. 3 is a diagram showing a pattern shape of a planar coil used in the planar inductor of the first example.
FIG. 4 is a view showing a pattern shape of a planar coil used in the planar inductor of the first example.
FIG. 5 is a diagram showing a schematic configuration of a planar transformer according to a second example.
FIG. 6 is a diagram showing a schematic configuration of a planar inductor according to a third example.
FIG. 7 is a diagram showing a configuration of a coil conductor used in a third example.
FIG. 8 is a diagram showing a change in magnetic permeability of a soft magnetic material used in a third example due to hard axis excitation and easy axis excitation.
FIG. 9 is a diagram showing an example in which a coil conductor used in a third example is disconnected.
FIG. 10 is a diagram showing a schematic configuration of a planar inductor using a third example of an elliptical spiral wound planar coil.
FIG. 11 is a diagram showing a schematic configuration of a planar inductor using a rectangular spiral wound planar coil of a third example.
FIG. 12 is a diagram illustrating a schematic configuration of a planar inductor using a serpentine planar coil according to a third example;
FIG. 13 is a diagram showing a schematic configuration of a planar inductor using two planar coils according to a third example.
FIG. 14 is a diagram showing a schematic configuration of a conventional planar inductor used for describing the first embodiment of the present invention.
FIG. 15 is a diagram showing a state where an eddy current is generated in a pad portion used for describing the first embodiment.
FIG. 16 is a view showing a schematic configuration of the planar inductor according to the first embodiment;
FIG. 17 is a diagram illustrating a schematic configuration of another planar inductor according to the first embodiment;
FIG. 18 is a diagram illustrating a schematic configuration of a pad portion used in the planar inductor according to the second embodiment of the present invention.
FIG. 19 is a diagram showing an example of a conventional planar inductor.
FIG. 20 is a diagram illustrating frequency characteristics of a conventional planar inductor.
FIG. 21 is a diagram showing another example of a conventional planar inductor.
FIG. 22 is a diagram showing frequency characteristics of a conventional planar inductor.
FIG. 23 is a diagram showing an example of a magnetic flux distribution in a device of a conventional planar inductor having a spiral coil pattern.
FIG. 24 is a diagram showing an example of a magnetic flux distribution in a device of a conventional planar inductor having a serpentine coil pattern.
FIG. 25 is a diagram for explaining an eddy current generated by an in-plane magnetic flux component of a soft magnetic material.
FIG. 26 is a diagram for explaining an eddy current generated by a vertical magnetic flux component of a soft magnetic material.
FIG. 27 is a diagram for explaining an eddy current in a coil conductor generated by a vertical magnetic flux component.
FIG. 28 is a view for explaining distribution of high-frequency current density in a coil conductor.
FIG. 29 is a diagram showing a relationship between a measured value and a calculated value of a coil resistance measured for a conventional planar inductor.
[Explanation of symbols]
11, 21, 31, 41, 51 ... planar coil,
111, 211, 212, 311, 312, 411, 412, 511, 512... Coil conductors;
11a, 11b, 11c, 211a, 211b, 211c, 212a, 212b, 212c ... conductor line,
12 ... insulator,
13, 22, 32, 42, 52 ... soft magnetic material.
71 ... plane coil,
711: hollow part,
72 ... plane coil,
731, 732, 83 ... soft magnetic material,
731a, 732a, 831 ... holes,
74, 81 ... pad part,
811 ... divided area,
82 ... cut,

Claims (2)

In a planar magnetic element in which one or more planar coils are sandwiched by magnetic materials via an insulator,
A planar magnetic element, wherein holes are formed in portions of the magnetic material corresponding to pads for connecting an external circuit of the planar coil. In a planar magnetic element in which one or more planar coils are sandwiched by magnetic materials via an insulator,
A planar magnetic element, wherein a plurality of cuts are made in a pad portion for connecting an external circuit of the planar coil from a peripheral edge thereof to form a divided region.

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