JP4156713B2

JP4156713B2 - Piezoelectric transformer

Info

Publication number: JP4156713B2
Application number: JP22007198A
Authority: JP
Inventors: 良明布田; 超史勝野
Original assignee: NEC Tokin Corp
Current assignee: Tokin Corp
Priority date: 1998-08-04
Filing date: 1998-08-04
Publication date: 2008-09-24
Anticipated expiration: 2018-08-04
Also published as: JP2000058937A

Description

【０００１】
【発明の属する技術分野】
本発明は、圧電性セラミックスを用いた圧電トランスに関し、特に圧電セラミックス矩形板と内部電極を矩形板の厚み方向に積層し、矩形板の長さ方向の共振を利用した圧電トランスに関するものである。
【０００２】
【従来の技術】
近年、ノート型パーソナルコンピュータや携帯ビデオカメラの普及に伴い画像表示システムとして液晶ユニットが普及し、液晶バックライトの点灯用にインバータが多用されている。このインバータには高電圧発生用に電磁式トランスが用いられているが、発生電磁ノイズの低減や低消費電力化、高効率化、機器の小型低背化などの要求により、電磁式卜ランスに代わつて圧電トランスの実用化が進みつつある。圧電トランスの電力伝送は双方２向性が有り、高電圧を入力し、降圧して低電圧を得る事も可能であり、圧電トランスを用いたＤＣ／ＤＣコンバータやＡＣアダプターの研究がなされている。
【０００３】
図７は従来のローゼンタイプλモード圧電トランスに用いられている圧電振動子の構造の概略斜視図である。図７において、圧電セラミックス矩形板３１には、長さ方向のおよそ半分の部分に厚さ方向に対向する電極３２、３３が形成されている。また、圧電セラミックス矩形板３１の電極３２、３３が形成された部分とは反対側の残り半分の部分は長さ方向の端面にに表面電極３４が形成されている。圧電セラミックス矩形板３１は、矢印で示すように、電極３２、３３の部分は矩形板厚さ方向に分極され、端面電極３４の間の部分は、矢印で示すように、圧電セラミックス矩形板の長さ向に分極されている。電極３２、３３間に矩形板の共振周波数近傍の電圧が印加されると、圧電横効果により矩形板は励振され、この時、電極３３と電極３４の間には圧電縦効果により電圧が発生する。ここで、電極３２、３３に印加した入力電圧と電極３４に発生した出力電圧について説明すると、電極３２、３３の対向電極の間隔は電極３３、３４の間隔に比べ十分に小さく、電極３２、３３の面積は電極３４の面積より十分に大きいため、入力側の静電容量は出力側の静電容量に比べ十分大きな値となる。従つて、入力側に低い電圧を印加して振動子を励振した場合、出力側には入力側電極の間隔と出力側電極間の間隔の比に比例し、入出力側のそれぞれの静電容量の比に逆比例した大きな電圧が発生する。圧電トランスの双方向性から電極３４に高電圧を印加して振動子を励振した場合、電極３２、３３では低電圧が得られる。
【０００４】
【発明が解決しようとする課題】
ローゼン型圧電トランスを基本とする矩形板の長さ方向の共振を利用した圧電トランスは各種の構造が提案、実用化されているが、いずれの構造も矩形板の長さ方向を振動のモードに応じて入力部と出力部に分割した構造である。したがって、矩形板に長さ振動を励振する際、矩形板の全長と入力部の長さの比はローゼン型で１／２、１．５波長モードでも２／３となり、実際に振動する長さより励振部の長さが小さくなるので、見かけの電気機械結合係数が小さくなり、励振効率が低下するという問題がある。またローゼン型を基本とする圧電トランスは入力部が圧電横効果を利用しているが、圧電縦効果を利用する事で効率の改善が期待できる。
【０００５】
また、出力部で効率よく機械振動エネルギーを電気エネルギーに変換するためには、負荷抵抗と出力部のインピーダンスマッチングが重要である。液晶バックライトの抵抗は１００ｋΩ程度なので、インピーダンスマッチングを取るための圧電トランスの出力部の制動容量値は数１０ｐＦ程度になり、矩形板の長さ方向両端面に電極を形成する事で構成が可能である。しかし、ＤＣ／ＤＣコンバータやＡＣアダプターでは負荷抵抗が数１０Ω以下なのでインピーダンスマッチングを取るための圧電トランスの出力部の制動容量値は数１０ｎＦになる。この制動容量を実現するため圧電縦効果を利用した構造が用いられ、そのために出力部を長さ方向に分極する必要が有る。このように大きな制動容量を実現するには、出力部も内部電極の積層構造とする必要が有る。
【０００６】
それ故に本発明の課題は、入力部に圧電縦効果を用いて電気的エネルギーと機械的エネルギーの変換効率を改善し、また負荷抵抗がＩＫΩ以下のときでも、圧電トランスの出力側の制動容量を容易に変化することが可能で、負荷抵抗とのマッチングが良好な構造の圧電トランスを提供することにある。
【０００７】
【課題を解決するための手段】
本発明によれば、セラミック矩形板の長さ方向の振動モードを利用した圧電トランスにおいて、前記セラミック矩形板の厚さ方向のほぼ半分の部分には、圧電縦効果を利用して前記セラミック矩形板を前記長さ方向に励振するため、前記長さ方向に直交して前記セラミック矩形板の幅方向の寸法に一致するようにのびた複数の入力部帯状内部電極がセラミック層を介して積層され、該入力部帯状内部電極が前記長さ方向で対向電極になるように複数の入力部外部電極群に接続され、前記セラミック矩形板の厚さ方向の残りの部分には、前記セラミック矩形板から圧電縦効果を利用して電力を取り出すため、前記長さ方向に直交して前記セラミック矩形板の幅方向の寸法に一致するようにのびた複数の出力部帯状内部電極がセラミック層を介して積層され、該出力部帯状内部電極が前記長さ方向で対向電極になるように複数の出力部外部電極群に接続されていることを特徴とする圧電トランスが得られる。
【０００８】
また、本発明によれば、セラミック矩形板の長さ方向の振動モードを利用した圧電トランスにおいて、前記セラミック矩形板の厚さ方向のほぼ半分の部分には、圧電縦効果を利用して前記セラミック矩形板を長さ方向に励振するため、前記長さ方向に直交してのびかつ前記長さ方向に繰り返す入力部交差指電極が複数積層され、該入力部交差指電極は前記セラミック矩形板の側面で第１及び第２の外部電極に接続され、前記セラミック矩形板の厚さ方向の残りの部分には、前記セラミック矩形板から圧電縦効果を利用して電力を取り出すため、前記長さ方向に直交してのびかつ前記長さ方向に繰り返す出力部交差指電極が複数積層され、該出力部交差指電極は前記セラミック矩形板の側面で第３及び第４の外部電極に接続されていることを特徴とする圧電トランスが得られる。
【０００９】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
【００１０】
図１〜図３は本発明の第１の実施の形態に係る圧電トランスを示す。この圧電トランスは圧電セラミックスよりなるセラミック矩形板１１の長さ方向の振動モードを利用したものである。
【００１１】
セラミック矩形板１１の厚さ方向のほぼ半分の部分、即ち、入力部には、圧電縦効果を利用してセラミック矩形板１１を前記長さ方向に励振するため、前記長さ方向に直交してセラミック矩形板１１の幅方向の寸法に一致するようにのびた複数の入力部帯状内部電極１２がセラミック層を介して積層されている。これらの入力部帯状内部電極１２は前記長さ方向で対向電極になるように複数の入力部外部電極１３群に接続されている。
【００１２】
セラミック矩形板１１の厚さ方向の残りの部分、即ち、出力部には、セラミック矩形板１１から圧電縦効果を利用して電力を取り出すため、前記長さ方向に直交してセラミック矩形板１１の幅方向の寸法に一致するようにのびた複数の出力部帯状内部電極１４がセラミック層を介して積層されている。これらの出力部帯状内部電極１２は前記長さ方向で対向電極になるように複数の出力部外部電極１５群に接続されている。
【００１３】
さらに実施例１をもって説明する。圧電セラミックスとしてはＰｂＴｉＯ₃−ＰｂＺｒＯ₃系材料を用い、長さ２２ｍｍ、幅５ｍｍ、厚さ１．２ｍｍの圧電トランスを試作した。入出力部である矩形板の圧電セラック層は厚さそれぞれ０．６ｍｍである。入力部は矩形板の長さ方向に直交し幅方向に貫通する幅０．２ｍｍの帯状内部電極を１ｍｍ間隔で１８本形成した厚み０．１ｍｍのセラミックス層を５層積層し、帯状内部電極が一本ずつ対向電極となるように対向する側面で複数の外部電極に接続した。出力部は長さ方向に直交し幅方向に貫通する幅０．１ｍｍの帯状電極を０．２５ｍｍ間隔で６０本配置したセラミック層を矩形板厚さ方向で０．１ｍｍ間隔で５層積層した。該帯状電極は長さ方向で一本ずつ対向電極となるように一層おきに側面で外部電極に接続した。
【００１４】
分極は温度１５０℃で、入力部印加電圧１ｋＶ−１５分間、出力部印可電圧２００Ｖ−１５分間それぞれ処理した。１波長共振モードを使用し、入力電圧１００Ｖｐｐ、負荷抵抗５０Ωの時の圧電トランス特性を測定した。測定結果を同一寸法の図７に示したローゼン構造からなる比較例と比較して表１に示した。
【００１５】
【表１】

【００１６】
図４〜図６は本発明の第２の実施の形態に係る圧電トランスを示す。この圧電トランスも、圧電セラミックスよりなるセラミック矩形板１１の長さ方向の振動モードを利用したものである。
【００１７】
セラミック矩形板２１の厚さ方向のほぼ半分の部分、即ち、入力部には、圧電縦効果を利用してセラミック矩形板２１を長さ方向に励振するため、前記長さ方向に直交してのびかつ前記長さ方向に繰り返す入力部交差指電極２４が複数積層されている。これらの入力部交差指電極２４はセラミック矩形板２１の側面で第１及び第２の外部電極２２に接続されている。
【００１８】
セラミック矩形板２１の厚さ方向の残りの部分、即ち、出力部には、セラミック矩形板２１から圧電縦効果を利用して電力を取り出すため、前記長さ方向に直交してのびかつ前記長さ方向に繰り返す出力部交差指電極２５が複数積層されている。これらの出力部交差指電極２５はセラミック矩形板２１の側面で第３及び第４の外部電２３極に接続されている。
【００１９】
さらに実施例２をもって説明する。圧電セラミックスとしてはＰｂＴｉＯ₃−ＰｂＺｒＯ₃系材料を用い、長さ２２ｍｍ、幅５ｍｍ、厚さ１．２ｍｍの圧電トランスを試作した。入出力部である矩形板の圧電セラック層は厚さそれぞれ０．６ｍｍである。入力部は矩形板の長さ方向に直交する長さ４ｍｍ、幅０．２ｍｍの交差指内部電極を１ｍｍ間隔で１８本形成した厚み０．１ｍｍのセラミックス層を５層積層し、交差指電極が露出する二側面でそれぞれの外部電極に接続した。出力部は長さ方向に直交する長さ４ｍｍ、幅０．１ｍｍの交差指内部電極を０．２５ｍｍ間隔で６０本配置したセラミック層を矩形板厚さ方向で０．１ｍｍ間隔で５層積層し、交差指電極が露出する二側面でそれぞれの外部電極に接続した。
【００２０】
分極は温度１５０℃、で入力部印可電圧１ｋＶ一１５分間、出力部印可電庄２００Ｖ−１５分間それぞれ処理した。１波長共振モードを使用し、入力電圧１００Ｖｐｐ、負荷抵抗２００Ωの時の圧電トランス特性を測定した。測定結果を同一寸法の第７図に示したローゼン構造からなる比較例と比較して表１に示した。
【００２１】
表１より分かるように、本発明の圧電トランスは降圧比は１０倍程度であり、入力電圧が１００Ｖの交流から７．５Ｖの交流に降圧するＡＣ−ＡＣコンバータが可能であり、更に、後段に整流回路を付加する事で５〜３Ｖの直流電圧を得るＡＣ−ＤＣコンバータを得る事が可能である。さらにインピーダンスのマッチングが良好のため９８％以上の高効率が達成されている。従来構造ではインピーダンスのマッチングが得られずＤＣＤＣコンバータ用トランスとしての特性は得られないことが明らかである。
【００２２】
【発明の効果】
以上説明したように、本発明における圧電トランスでは、セラミック矩形板に長さ方向の振動を励振するのに、セラミック矩形板に厚さ方向のほぼ半分の入力部に、帯状電極や交差指電極を形成し、圧電縦効果を利用してセラミック矩形板を励振するより、高効率で機械振動を励振する事が可能である。
【００２３】
また、本発明の圧電トランスではセラミック矩形板に厚さ方向のほぼ半分の出力部に圧電縦効果を用い、長さ方向に帯状電極や交差指電極を複数配列し、出力部を長さ方向に分割した構造であるため、インピーダンスマッチングを得るための出力側制動容量の値の調整が可能である。
【００２４】
したがって本発明よれば、１００Ω程度の負荷に対して、１０数倍の降圧比が得られ、効率が９８％以上と優れた構造の圧電トランスを提供することが可能である。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態に係る圧電トランスの斜視図である。
【図２】図１の圧電トランスの入力部の長さ方向に直交する帯状電極を含む断面図である。
【図３】図１の圧電トランスの出力部の長さ方向に直交する帯状電極を含む断面図である。
【図４】本発明の第２の実施の形態に係る圧電トランスの斜視図である。
【図５】図４の圧電トランスの入力部の長さ方向に直交する帯状電極を含む断面図である。
【図６】図４の圧電トランスの出力部の長さ方向に直交する帯状電極を含む断面図である。
【図７】従来の圧電トランスの斜視図である。
【符号の説明】
１１セラミック矩形板
１２入力部帯状内部電極
１３入力部外部電極
１４出力部帯状内部電極
１５出力部外部電極
２１セラミック矩形板
２２第１及び第２の外部電極
２３第３及び第４の外部電
２４入力部交差指電極
２５出力部交差指電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric transformer using piezoelectric ceramics, and more particularly to a piezoelectric transformer in which piezoelectric ceramic rectangular plates and internal electrodes are laminated in the thickness direction of the rectangular plates and the resonance in the length direction of the rectangular plates is utilized.
[0002]
[Prior art]
In recent years, with the spread of notebook personal computers and portable video cameras, liquid crystal units have become widespread as image display systems, and inverters are frequently used for lighting liquid crystal backlights. This inverter uses an electromagnetic transformer to generate high voltage, but due to demands such as reduction of generated electromagnetic noise, low power consumption, high efficiency, and reduction in the size and height of equipment, the electromagnetic transformer lance is used. Instead, the practical use of piezoelectric transformers is progressing. Piezoelectric transformers have bi-directional power transmission, and high voltage can be input and stepped down to obtain low voltage. Research on DC / DC converters and AC adapters using piezoelectric transformers has been made. .
[0003]
FIG. 7 is a schematic perspective view of the structure of a piezoelectric vibrator used in a conventional Rosen-type λ mode piezoelectric transformer. In FIG. 7, the piezoelectric ceramic rectangular plate 31 is formed with electrodes 32 and 33 facing in the thickness direction at approximately half of the length direction. Further, a surface electrode 34 is formed on the end face in the length direction of the remaining half of the piezoelectric ceramic rectangular plate 31 on the opposite side to the portion where the electrodes 32 and 33 are formed. In the piezoelectric ceramic rectangular plate 31, as shown by the arrows, the portions of the electrodes 32 and 33 are polarized in the rectangular plate thickness direction, and the portion between the end face electrodes 34 is the length of the piezoelectric ceramic rectangular plate as shown by the arrows. Polarized in the direction. When a voltage near the resonance frequency of the rectangular plate is applied between the electrodes 32 and 33, the rectangular plate is excited by the piezoelectric lateral effect, and at this time, a voltage is generated between the electrode 33 and the electrode 34 by the piezoelectric longitudinal effect. . Here, the input voltage applied to the electrodes 32 and 33 and the output voltage generated at the electrode 34 will be described. The distance between the opposing electrodes of the electrodes 32 and 33 is sufficiently smaller than the distance between the electrodes 33 and 34, and the electrodes 32 and 33. Is sufficiently larger than the area of the electrode 34, the capacitance on the input side is sufficiently larger than the capacitance on the output side. Therefore, when a vibrator is excited by applying a low voltage to the input side, the capacitance on the input / output side is proportional to the ratio of the interval between the input side electrode and the interval between the output side electrodes on the output side. A large voltage that is inversely proportional to the ratio is generated. When the vibrator is excited by applying a high voltage to the electrode 34 due to the bidirectional nature of the piezoelectric transformer, a low voltage is obtained at the electrodes 32 and 33.
[0004]
[Problems to be solved by the invention]
Various structures have been proposed and put to practical use for piezoelectric transformers that utilize resonance in the length direction of a rectangular plate based on a Rosen-type piezoelectric transformer, but each structure uses the length direction of the rectangular plate as a vibration mode. Accordingly, the structure is divided into an input unit and an output unit. Therefore, when exciting the length vibration to the rectangular plate, the ratio of the total length of the rectangular plate to the length of the input part is 1/2 for Rosen type and 2/3 for the 1.5 wavelength mode. Since the length of the excitation unit is reduced, there is a problem that the apparent electromechanical coupling coefficient is reduced and the excitation efficiency is lowered. In addition, in the piezoelectric transformer based on the Rosen type, the input portion uses the piezoelectric lateral effect. However, improvement in efficiency can be expected by using the piezoelectric longitudinal effect.
[0005]
Moreover, in order to efficiently convert mechanical vibration energy into electrical energy at the output section, impedance matching between the load resistance and the output section is important. Since the resistance of the liquid crystal backlight is about 100 kΩ, the braking capacitance value of the output part of the piezoelectric transformer for impedance matching is about several tens of pF, and it can be configured by forming electrodes on both end faces of the rectangular plate in the length direction. It is. However, since the load resistance of the DC / DC converter or the AC adapter is several tens of ohms or less, the braking capacity value of the output part of the piezoelectric transformer for impedance matching is several tens of nF. In order to realize this braking capacity, a structure using the piezoelectric longitudinal effect is used, and for this purpose, the output section needs to be polarized in the length direction. In order to realize such a large braking capacity, the output unit also needs to have a laminated structure of internal electrodes.
[0006]
Therefore, the object of the present invention is to improve the conversion efficiency of electrical energy and mechanical energy by using the piezoelectric longitudinal effect at the input section, and to reduce the braking capacity on the output side of the piezoelectric transformer even when the load resistance is IKΩ or less. It is an object of the present invention to provide a piezoelectric transformer that can be easily changed and has a good matching with a load resistance.
[0007]
[Means for Solving the Problems]
According to the present invention, in the piezoelectric transformer using the vibration mode in the length direction of the ceramic rectangular plate, the ceramic rectangular plate is formed on the almost half portion in the thickness direction of the ceramic rectangular plate using the piezoelectric longitudinal effect. A plurality of input portion strip-like internal electrodes extending in a direction perpendicular to the length direction so as to coincide with the dimension in the width direction of the ceramic rectangular plate are laminated via a ceramic layer, The input portion strip-like internal electrode is connected to a plurality of input portion external electrode groups so as to be counter electrodes in the length direction, and the remaining portion in the thickness direction of the ceramic rectangular plate is connected to the piezoelectric vertical plate from the ceramic rectangular plate. In order to take out electric power using the effect, a plurality of output band-like internal electrodes extending through the ceramic layer so as to coincide with the widthwise dimension of the ceramic rectangular plate perpendicular to the length direction. Laminated piezoelectric transformer is obtained, wherein a output unit strip internal electrodes are connected to a plurality of output portions external electrode group so that the counter electrode in the length direction.
[0008]
Further, according to the present invention, in the piezoelectric transformer using the vibration mode in the length direction of the ceramic rectangular plate, the ceramic rectangular plate is used for the half of the ceramic rectangular plate in the thickness direction by using the piezoelectric longitudinal effect. In order to excite the rectangular plate in the length direction, a plurality of input portion cross finger electrodes extending perpendicularly to the length direction and repeating in the length direction are laminated, and the input portion cross finger electrodes are arranged on the side surfaces of the ceramic rectangular plate. Connected to the first and second external electrodes, and the remaining portion in the thickness direction of the ceramic rectangular plate is used to extract electric power from the ceramic rectangular plate using the piezoelectric longitudinal effect. A plurality of output part cross finger electrodes extending perpendicularly and repeating in the length direction are stacked, and the output part cross finger electrodes are connected to the third and fourth external electrodes on the side surface of the ceramic rectangular plate. Special A piezoelectric transformer is obtained and.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0010]
1 to 3 show a piezoelectric transformer according to a first embodiment of the present invention. This piezoelectric transformer uses a vibration mode in the length direction of a ceramic rectangular plate 11 made of piezoelectric ceramics.
[0011]
In order to excite the ceramic rectangular plate 11 in the length direction by using the piezoelectric longitudinal effect, the ceramic rectangular plate 11 is excited in the longitudinal direction at a substantially half portion in the thickness direction of the ceramic rectangular plate 11, that is, in the input portion. A plurality of input portion strip-like internal electrodes 12 extending so as to coincide with the widthwise dimension of the ceramic rectangular plate 11 are laminated via a ceramic layer. These input part strip | belt-shaped internal electrodes 12 are connected to the several input part external electrode 13 group so that it may become a counter electrode in the said length direction.
[0012]
In order to extract electric power from the ceramic rectangular plate 11 using the piezoelectric longitudinal effect, the remaining portion in the thickness direction of the ceramic rectangular plate 11, that is, the output portion, is orthogonal to the length direction of the ceramic rectangular plate 11. A plurality of output portion strip-like internal electrodes 14 extending so as to coincide with the dimension in the width direction are laminated via a ceramic layer. These output part strip | belt-shaped internal electrodes 12 are connected to the several output part external electrode 15 group so that it may become a counter electrode in the said length direction.
[0013]
Further description will be made with reference to the first embodiment. With PbTiO ₃ -PbZrO ₃ based material as the piezoelectric ceramic was fabricated a length 22 mm, width 5 mm, a thickness of 1.2mm piezoelectric transformer. The piezoelectric shellac layers of the rectangular plate that is the input / output unit are each 0.6 mm in thickness. The input part was formed by laminating five ceramic layers each having a thickness of 0.1 mm, in which 18 strip-like internal electrodes having a width of 0.2 mm penetrating in the width direction perpendicular to the length direction of the rectangular plate were formed at intervals of 1 mm. It connected to the some external electrode by the side surface which opposes so that it may become a counter electrode one by one. The output part was formed by laminating five ceramic layers each having a width of 0.1 mm, which is perpendicular to the length direction and penetrating in the width direction, at a distance of 0.1 mm in the rectangular plate thickness direction. The strip-like electrodes were connected to the external electrodes on the side surfaces every other layer so as to be opposed electrodes one by one in the length direction.
[0014]
Polarization was performed at a temperature of 150 ° C., with an input portion applied voltage of 1 kV-15 minutes and an output portion applied voltage of 200 V-15 minutes. Using the one-wavelength resonance mode, the piezoelectric transformer characteristics were measured when the input voltage was 100 Vpp and the load resistance was 50Ω. The measurement results are shown in Table 1 in comparison with the comparative example having the Rosen structure shown in FIG.
[0015]
[Table 1]

[0016]
4 to 6 show a piezoelectric transformer according to a second embodiment of the present invention. This piezoelectric transformer also uses a vibration mode in the length direction of the ceramic rectangular plate 11 made of piezoelectric ceramics.
[0017]
In order to excite the ceramic rectangular plate 21 in the length direction by using the piezoelectric longitudinal effect, the ceramic rectangular plate 21 extends in a direction perpendicular to the length direction in the almost half of the ceramic rectangular plate 21 in the thickness direction, that is, in the input portion. A plurality of input portion cross finger electrodes 24 that repeat in the length direction are stacked. These input portion cross finger electrodes 24 are connected to the first and second external electrodes 22 on the side surfaces of the ceramic rectangular plate 21.
[0018]
In order to extract electric power from the ceramic rectangular plate 21 by using the piezoelectric longitudinal effect, the remaining portion in the thickness direction of the ceramic rectangular plate 21, that is, the output portion extends perpendicularly to the length direction and the length. A plurality of output unit cross finger electrodes 25 that repeat in the direction are stacked. These output unit cross finger electrodes 25 are connected to the third and fourth external electrodes 23 on the side surface of the ceramic rectangular plate 21.
[0019]
Further, a second embodiment will be described. A piezoelectric transformer having a length of 22 mm, a width of 5 mm, and a thickness of 1.2 mm was prototyped using a PbTiO ₃ —PbZrO ₃ -based material as the piezoelectric ceramic. The piezoelectric shellac layers of the rectangular plate that is the input / output unit are each 0.6 mm in thickness. The input part is formed by laminating five ceramic layers each having a thickness of 0.1 mm, in which 18 cross-finger internal electrodes having a length of 4 mm and a width of 0.2 mm perpendicular to the length direction of the rectangular plate are formed at intervals of 1 mm. The two exposed side surfaces were connected to each external electrode. The output part was formed by laminating 5 ceramic layers each having a length of 4 mm perpendicular to the length direction and a width of 0.1 mm and having 60 crossed finger internal electrodes arranged at intervals of 0.25 mm at intervals of 0.1 mm in the thickness direction of the rectangular plate. , And connected to each external electrode on the two side surfaces where the interdigitated electrodes are exposed.
[0020]
Polarization was performed at a temperature of 150 ° C. for 1 minute at an input voltage of 1 kV and for 15 minutes at an output voltage of 200 V for 15 minutes. Using the one-wavelength resonance mode, the piezoelectric transformer characteristics at an input voltage of 100 Vpp and a load resistance of 200Ω were measured. The measurement results are shown in Table 1 in comparison with the comparative example having the Rosen structure shown in FIG. 7 having the same dimensions.
[0021]
As can be seen from Table 1, the step-down ratio of the piezoelectric transformer of the present invention is about 10 times, and an AC-AC converter that steps down the input voltage from an alternating current of 100 V to an alternating current of 7.5 V is possible. It is possible to obtain an AC-DC converter that obtains a DC voltage of 5 to 3 V by adding a rectifier circuit. Furthermore, since the impedance matching is good, a high efficiency of 98% or more is achieved. It is obvious that impedance matching cannot be obtained with the conventional structure, and characteristics as a DCDC converter transformer cannot be obtained.
[0022]
【The invention's effect】
As described above, in the piezoelectric transformer according to the present invention, in order to excite the vibration in the length direction on the ceramic rectangular plate, the strip-like electrode and the cross finger electrode are provided in the input portion of the ceramic rectangular plate in almost half the thickness direction. It is possible to excite mechanical vibration with higher efficiency than to form and excite a ceramic rectangular plate using the piezoelectric longitudinal effect.
[0023]
Further, in the piezoelectric transformer of the present invention, a piezoelectric rectangular effect is applied to the ceramic rectangular plate at the output portion that is almost half of the thickness direction, a plurality of strip electrodes and cross finger electrodes are arranged in the length direction, and the output portion is set in the length direction. Since the structure is divided, it is possible to adjust the value of the output side braking capacity to obtain impedance matching.
[0024]
Therefore, according to the present invention, it is possible to provide a piezoelectric transformer having an excellent structure in which a step-down ratio of a factor of 10 is obtained for a load of about 100Ω and efficiency is 98% or more.
[Brief description of the drawings]
FIG. 1 is a perspective view of a piezoelectric transformer according to a first embodiment of the present invention.
2 is a cross-sectional view including a strip electrode perpendicular to the length direction of the input portion of the piezoelectric transformer of FIG. 1;
3 is a cross-sectional view including a strip-shaped electrode orthogonal to the length direction of the output portion of the piezoelectric transformer of FIG. 1;
FIG. 4 is a perspective view of a piezoelectric transformer according to a second embodiment of the present invention.
5 is a cross-sectional view including a strip electrode perpendicular to the length direction of the input portion of the piezoelectric transformer of FIG. 4;
6 is a cross-sectional view including a strip electrode perpendicular to the length direction of the output portion of the piezoelectric transformer of FIG. 4;
FIG. 7 is a perspective view of a conventional piezoelectric transformer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Ceramic rectangular plate 12 Input part strip | belt-shaped internal electrode 13 Input part external electrode 14 Output part strip | belt-shaped internal electrode 15 Output part external electrode 21 Ceramic rectangular plate 22 1st and 2nd external electrode 23 3rd and 4th external electric power 24 Input Cross finger electrode 25 Output cross finger electrode

Claims

In the piezoelectric transformer using the vibration mode in the length direction of the ceramic rectangular plate, the ceramic rectangular plate is placed in the length direction by using a piezoelectric longitudinal effect in a substantially half portion of the thickness direction of the ceramic rectangular plate. In order to excite, a plurality of input section strip-like internal electrodes extending so as to be perpendicular to the length direction and coincide with the width direction dimensions of the ceramic rectangular plate are stacked via a ceramic layer, It is connected to a plurality of input part external electrode groups so as to be opposed electrodes in the length direction, and the remaining portion in the thickness direction of the ceramic rectangular plate is powered by the piezoelectric longitudinal effect from the ceramic rectangular plate. In order to take out, a plurality of output-port strip-like internal electrodes extending so as to be perpendicular to the length direction and coincide with the width-direction dimension of the ceramic rectangular plate are laminated via a ceramic layer. Piezoelectric transformer is part strip internal electrodes, characterized in that it is connected to a plurality of outputs external electrode group so that the counter electrode in the length direction.

In the piezoelectric transformer using the vibration mode in the length direction of the ceramic rectangular plate, the ceramic rectangular plate is excited in the length direction by using the piezoelectric longitudinal effect in the almost half of the thickness direction of the ceramic rectangular plate. Therefore, a plurality of input part cross finger electrodes extending perpendicularly to the length direction and repeating in the length direction are stacked, and the input part cross finger electrodes are formed on the side surfaces of the ceramic rectangular plate by the first and second external electrodes. The remaining portion of the ceramic rectangular plate in the thickness direction is connected to the electrode, and the electric power is extracted from the ceramic rectangular plate using the piezoelectric longitudinal effect. A piezoelectric transformer, wherein a plurality of output unit cross finger electrodes that repeat in a direction are stacked, and the output unit cross finger electrodes are connected to third and fourth external electrodes on a side surface of the ceramic rectangular plate.