JPH10135532A - Piezoelectric transformer - Google Patents

Abstract

(57) [Problem] To provide a piezoelectric transformer which can obtain a high step-up ratio or step-down ratio and is easily supported. SOLUTION: An input-side piezoelectric section 10 and an output-side piezoelectric section 30 are overlapped and coupled in a vibration direction, and are supported and fixed in a direction orthogonal to the vibration direction. When an AC voltage 22 having a resonance frequency of the vibrating body 12 is applied between the excitation electrodes 14 and 16 on the input side piezoelectric unit 10 side, the vibration in the arrow FB direction is caused by the coupling coefficient d15 larger than the coupling coefficients d31 and d33. Then, the vibrating body 12 expands and contracts in the same direction. These vibrations,
When the expansion and contraction is transmitted to the output-side piezoelectric section 30 through the connecting portion of the vibrators 12, 32, the vibrator 32 also vibrates in the direction of arrow FB on the output side. Due to this vibration, the coupling coefficient d15
As a result, a voltage 42 is generated. The voltage 42 is extracted from the extraction electrodes 34 and 36.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer, and more specifically, to an improvement in a vibrating body structure.

[0002]

2. Description of the Related Art Piezoelectric transformers have a higher energy density than conventional winding transformers, and can be made smaller and thinner. (2) The switching frequency can be increased. (3) No electromagnetic noise. (4) The influence of heat generation is also reduced. There are such advantages, and research is progressing in various fields.

For example, Japanese Patent Application Laid-Open No. 4-167504 (known example 1) discloses a piezoelectric ceramic transformer which operates at 500 kHz or more by laminating piezoelectric ceramic disks. IEICE Technical Report
In PE92-68 (1993-02), pp. 25 to 31 (known example 2), an equivalent circuit of a thickness vertical vibration type piezoelectric transformer is considered. The same technical report PE93-19 (1993-07), pp. 51 to 55 (known example 3) discloses a piezoelectric transformer converter in which the efficiency of switching of a piezoelectric transformer is improved by a soft switching method. Technical report US95-21, EMD95-17, CPM95-29 (1995-07), P
9 to 16 (known example 4) disclose a laminated integrated sintering type piezoelectric transformer capable of obtaining a large step-up ratio (or step-down ratio). Technical report US95-22, EMD95-18, CPM95-30 (1
993-02), pages 17 to 21 (known example 5) disclose a piezoelectric transformer for a cold-cathode tube, which is driven by a voltage twice the power supply voltage using a full bridge circuit.

FIG. 6A shows a Rosen-type piezoelectric transformer, in which electrodes 112 and 114 are formed on the upper and lower (front and back) surfaces on the left side of a plate-shaped vibrating body 110, respectively, and on the right side. An electrode 116 is formed on the end face. The polarization directions of the vibrating body 110 are directions indicated by arrows, respectively, that is, a vertical direction on the left side and a horizontal direction on the right side.

[0005] The step-up ratio of such a piezoelectric transformer is expressed by using a coupling coefficient. The length of the input side and the output side is L, the thickness is T, the coupling coefficient of the piezoelectric lateral effect on the input side is d31, the coupling coefficient of the piezoelectric longitudinal effect on the output side is d33, the input voltage is Vin, the output voltage is Vout, Assuming that the quality factor is Qm, Vout / Vin is proportional to d31.d33.Qm. (L / T). Therefore, a piezoelectric transformer having a higher step-up ratio can be obtained as the coupling coefficients d31, d33 and Qm are larger. By the way, the conventional piezoelectric transformer has a configuration using the coupling coefficient d31 of the horizontal effect or the coupling coefficient d33 of the vertical effect as described above. Therefore, the upper limit of the boost ratio is determined by those coefficients, and it is not possible to obtain a boost ratio higher than that.

Next, the piezoelectric transformer is supported at a node of vibration determined by the vibration mode, that is, at a node point having an amplitude of "0" so as not to hinder the mechanical vibration of the vibrating body formed of the piezoelectric material. In the case of the piezoelectric transformer of FIG. 6A, the vibration amplitude in the first mode is as shown in FIG. 6B, and the node point is the center PC. Therefore, the vibrating body 110
In order not to hinder the vibration of the vibrating body 1
10 must be supported.

The present invention has been made in view of such a point, and has as its object to obtain a piezoelectric transformer which can obtain a high step-up ratio or step-down ratio and can be easily supported.

[0008]

In order to achieve the above object, according to the present invention, a polarization is applied in a first direction, and a first vibration vibrates in a direction oblique to the first direction. A body, and a second vibrating body that is polarized in a second direction orthogonal to the first direction and vibrates in a direction oblique to the second direction; Along the first
And the second vibrating body is overlapped and coupled, and the vibrating bodies are fixed from a direction orthogonal to the vibration direction.

According to another aspect of the present invention, there are provided first and second vibrators which are polarized in a first direction and vibrate in a direction oblique to the first direction. Along with joining the first and second vibrators along the direction of
The vibrating body is fixed from a direction perpendicular to the vibration direction.

According to still another aspect of the present invention, a polarizing electrode is formed by laminating a vibrating body that is polarized in a longitudinal direction among the vibrating bodies. Further, the first vibrators are symmetrically stacked with the second vibrator interposed therebetween.

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings.

[0012]

Embodiments of the present invention will be described below in detail with reference to examples. The piezoelectric transformer according to the present invention is suitable for, for example, a lighting power supply of a cold cathode fluorescent lamp used as a backlight light source in a notebook computer.

[0013]

First Embodiment First, a first embodiment will be described with reference to FIGS. FIG. 1A shows a front view of the first embodiment. As shown in the figure, in the piezoelectric transformer of this embodiment, a vibrating body on the input side (primary side) and a vibrating body on the output side (secondary side) are divided, and both are formed using an adhesive or the like. The joining forms a piezoelectric transformer. Which of the input side or output side is
The setting may be made according to the necessity of step-up and step-down, but in the following description, the upper side is the input side, and the lower side is the output side.

First, as shown in FIG. 1B, the input-side piezoelectric section 10 has excitation electrodes 14 and 16 formed on the upper and lower surfaces of a plate-shaped vibrating body 12, respectively, and further has polarization on both left and right ends. Electrodes 18 and 20 are formed. Polarizing electrode 1
A DC voltage for polarization is applied to 8 and 20, whereby the vibrating body 12 is polarized in the direction of arrow FA. When a driving AC voltage 22 is applied to the excitation electrodes 14 and 16, the vibrating body 12 vibrates and expands and contracts as indicated by a dotted line in the direction of arrow FB. The coupling coefficient in this case is d15.

FIG. 2 shows the relationship between the coefficient and the direction of polarization or vibration. The polarization direction of the vibrating body 100 is indicated by an arrow fa. The coupling coefficient d33 is for the case where the vibrating body 100 vibrates in the same or parallel direction as the polarization direction fa.
The coupling coefficient d31 is when the vibrating body 100 vibrates in a direction orthogonal to the polarization direction fa. On the other hand, the coupling coefficient d
Reference numeral 15 denotes a case where the vibration is performed in a direction oblique to the polarization direction fa. The same applies to the coupling coefficient of the vibrating body of the output-side piezoelectric section described later.

Next, as shown in FIG. 1 (C), the output side piezoelectric section 30 has extraction electrodes 34 and 36 formed on the left and right ends of a plate-shaped vibrator 32, respectively. Electrodes 38 and 40 are formed, respectively. A DC voltage for polarization is applied to the electrodes for polarization 38 and 40, whereby the vibrating body 32 is polarized in the direction of arrow FC. When the input side piezoelectric section 10 vibrates in the direction of arrow FB, the mechanical energy thereof is transmitted to the output side piezoelectric section 30 and the vibrating body 32
Also vibrate and expand and contract as indicated by the dotted line in the direction of arrow FB. The coupling coefficient of this vibration is d15. Due to this vibration, electric energy is generated in the lateral direction, and an output voltage 42 is output from the extraction electrodes 34 and 36.

The polarization electrodes 18, 20, 38, and 40 of the input-side piezoelectric section 10 and the output-side piezoelectric section 30 are connected to the vibrating body 1.
The poles 2 and 32 are polarized in a predetermined direction, and need not necessarily be polarized if they are polarized in some way.

Next, the input-side piezoelectric section 1 having the above-described configuration will be described.
0 and the output side piezoelectric unit 30 are, as shown in FIG.
The upper and lower parts are joined by an adhesive or the like, and are further fixed by fixing bases 44 and 46. FIG. 3 shows various shapes of the fixing bases 44 and 46. In the example shown in FIG. 7A, a spindle-shaped projection 48 is formed on the piezoelectric base contact side of the fixing bases 44, 46. In the example shown in FIG. 3B, two columnar projections 50 are formed. The protrusion 50 is formed along the longitudinal direction of the vibrator. In the example shown in FIG. 3C, a square pillar-shaped projection 52 is formed. The projection 52 is formed along the longitudinal direction of the vibrator. The example shown in FIG. 3D is an example of a projection 54 in which the width of the projection 52 is increased. These projections are provided on the excitation electrode 14 of the vibrating body 12 or the vibrating body 3
Abut on the second polarization electrode 40.

Next, the operation of this embodiment will be described. When an AC voltage 22 having the resonance frequency of the vibrating body 12 is applied between the excitation electrodes 14 and 16 in the input-side piezoelectric section 10, vibration occurs in the direction of arrow FB due to the electromechanical coupling coefficient d15.
The vibrating body 12 expands and contracts in the same direction. These vibrations and expansions and contractions are caused by the connecting portions of the vibrators 12 and 32 on the output side piezoelectric unit 30.
Is transmitted to the vibrating body 32 in the direction of arrow FB on the output side.
Vibration occurs. Due to this vibration, the electromechanical coupling coefficient d
The voltage 42 is generated by 15. This voltage 42 is extracted from the electrodes 34 and 36.

As described above, according to the present embodiment, unlike the above-described background art, the voltage is raised or lowered with the coupling coefficient d15 when vibrating in a direction oblique to the polarization direction. As a general material characteristic, the coupling coefficient d15 is larger than the coupling coefficients d31 and d33. Therefore, the above-described step-up ratio or step-down ratio also increases. Further, according to the present embodiment, since the vibrating body is supported from a direction orthogonal to the vibration direction,
There is also an advantage that the vibrator can be easily fixed and supported. Further, the vibrating body is formed separately on the input side and the output side, and these are combined to form a piezoelectric transformer. Therefore, polarization can be separately and independently performed on the input side and the output side.

[0021]

Second Embodiment Next, a second embodiment will be described with reference to FIG. In the embodiment shown in FIG.
The polarization direction of the vibrating body 62 is the same as the arrow FA direction of the input-side piezoelectric unit 10. That is, the electrodes 64 and 66 serve both as a polarization electrode and an extraction electrode. A spacer 68 is provided between the input-side piezoelectric section 10 and the fixing base 46.
Is provided. In this embodiment, the coupling coefficient on the output side is g31. Therefore, a higher step-up ratio or step-down ratio than before can be obtained, though slightly lower than in the first embodiment.

Next, the embodiment shown in FIG. 1B is for easily performing polarization. A plurality of internal electrodes 70 are formed inside the above-described vibrating body 12 so as to be stacked along the left-right direction of the drawing, that is, in the length direction. Internal electrode 7
0 is alternately connected to the electrodes 72 and 74, respectively. Then, by applying a DC voltage to the electrodes 72 and 74, the vibrating body 12 is polarized in the direction of the arrow FA which is the laminating direction of the internal electrodes 70. Any one of the internal electrodes 7
Focusing on 0, the direction of the electric field is reversed on the left and right sides, and the polarization direction is also reversed. With such a laminated structure, polarization in the longitudinal direction of the vibrating body 12 can be performed at a relatively low voltage. In this example, the electrodes 72 and 74 also serve as a polarization electrode and an excitation electrode. The vibrating body of the output-side piezoelectric section shown in FIG. 4A may have the same laminated structure.

The embodiment shown in FIG. 3C is obtained by covering the electrodes 72 and 74 of the embodiment shown in FIG. By doing so, there is an advantage that the spacer 68 of FIG. 4A becomes unnecessary and the number of parts can be reduced.

[0024]

Third Embodiment Next, a third embodiment will be described with reference to FIG. In this embodiment, the input side piezoelectric section is provided symmetrically with the output side piezoelectric section interposed therebetween. Since the basic configuration of the input side piezoelectric section is the same as that of the above-described embodiment, one side is denoted by reference numeral A and the other side is denoted by reference numeral B. The output-side piezoelectric section is the same as in the above-described embodiment.

The vibrating body 12 of the input side piezoelectric units 10A and 10B
The thicknesses of A and 12B are の of the above-described embodiment, and the AC voltages 22A and 22B are in opposite phases.
That is, in the above-described embodiment, the mechanical vibration is applied from one side of the output-side piezoelectric section 30, but in the present embodiment, the mechanical vibration is applied in opposite phases from both sides. According to this embodiment, in addition to the effect of the above-described embodiment, an effect that the boost ratio is improved can be obtained. The polarization directions of the vibrators 12A and 12B may be reversed, and the AC voltages 22A and 22B may have the same phase.

[0026]

Other Embodiments There are many embodiments of the present invention, and various modifications can be made based on the above disclosure. For example, the following is also included. (1) In the above embodiment, the case where the present invention is applied to a flat-plate type piezoelectric transformer has been described. However, the present invention can be applied to various types of vibrating bodies such as quadrangular prisms. Further, it is not necessary to match the shape of the vibrating body on the input side and the output side. (2) The shape and arrangement of the electrodes of the vibrating body, and the directions of polarization and vibration may also be appropriately set as necessary. Which of the piezoelectric units is to be used as the input side or the output side may be set based on the relationship between step-up and step-down.

[0027]

As described above, the present invention has the following effects. (1) Since the vibrating body is caused to vibrate in a direction oblique to the polarization direction, a high step-up ratio or step-down ratio can be obtained. (2) Since the vibrating members are overlapped and coupled along the vibration direction and are supported from a direction perpendicular to the vibration direction, the vibrating members can be easily supported.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention. (A) is a front view, (B) is a cross-sectional view on the input side, and (C) is a cross-sectional view on the output side.

FIG. 2 is a diagram illustrating vibration directions according to the first embodiment and the background art.

FIG. 3 is a diagram illustrating various examples of a fixing base according to the first embodiment.

FIG. 4 is a diagram showing a second embodiment. (A) is a front view,
(B) and (C) are sectional views.

FIG. 5 is a front view showing a third embodiment.

FIG. 6 is a diagram illustrating an example of the configuration and amplitude of a Rosen-type piezoelectric transformer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Input side piezoelectric part 12, 32, 62, 100 ... Vibration body 14, 16 ... Exciting electrode 18, 20, 38, 40, 72, 74 ... Polarizing electrode 22 ... AC voltage 30, 60 ... Output side piezoelectric part 34, 36 ... Extraction electrode 42 ... Output voltage 44, 46 ... Fixing base 48, 50, 52, 54 ... Protrusion 64, 66 ... Electrode 68 ... Spacer 70 ... Internal electrode 76 ... Insulating film FA, FC, fa ... Polarization Direction FB: Vibration, expansion and contraction direction k31, k33, k15: Coupling coefficient

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Daisuke Kaino 6-16-20 Ueno, Taito-ku, Tokyo Taiyo Denki Co., Ltd.

Claims (4)

[Claims] A first vibrating body that is polarized in a first direction and vibrates in a direction oblique to the first direction; a second vibrating body that is polarized in a second direction orthogonal to the first direction. And a second vibrating body that vibrates in a direction oblique to the second direction; the first and second vibrating bodies are overlapped and coupled along the first direction and vibrated. A piezoelectric transformer characterized in that these vibrators are fixed from a direction perpendicular to the direction. 2. The first and second vibrators are polarized in a first direction and vibrate in a direction oblique to the first direction.
A piezoelectric transformer, wherein the first and second vibrators are overlapped and coupled along the first direction, and the vibrators are fixed from a direction perpendicular to the vibration direction. 3. The piezoelectric transformer according to claim 1, wherein a polarizing electrode is laminated on a vibrating body that is polarized in a length direction among the vibrating bodies. 4. The apparatus according to claim 1, wherein said first vibrator is symmetrically overlapped with a second vibrator interposed therebetween.
4. The piezoelectric transformer according to 2 or 3.