JPH10135533A - Piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily supportable piezoelectric transformer having a high vibration efficiency. SOLUTION: When the AC voltage 20 of resonance frequency of the oscillation body 10, which is polarized in the direction of arrows FA and FB, is applied between electrodes 12 and 14, longitudinal oscillation is generated in the direction of arrow FC by a coupling coefficient d31, and the oscillation body is extended and contracted in the direction shown by an arrow FD. When these oscillation, extension and contraction are transmitted to the output side of the oscillation body 10, longitudinal oscillation of the oscillation body 10 is generated in the direction of an arrow FE, voltage 22 is created by a coupling coefficient g31, and the voltage is taken out from electrodes 16 and 18. As the oscillation body 10 is oscillated in the secondary oscillation mode, the mode of oscillation is present in two places, and the oscillation body can be supported easily. Especially, if the node of free oscillation is supported, a high oscillation efficiency can be obtained, because oscillation is not disturbed.

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 particularly, to an improvement in the efficiency of a vibrating body.

[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. 5A 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, and the electrodes 112 and 114 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] By the way, the piezoelectric transformer has a node of vibration determined by the vibration mode, that is, an amplitude of "0", so as not to hinder the mechanical vibration of the vibrating body formed of the piezoelectric material.
Is supported at the nodal point. In the case of the piezoelectric transformer of FIG. 5A, the vibration amplitude in the first mode is as shown in FIG. 5B, and the node point is the center PQ. Therefore, the vibrating body 11
In order not to disturb the zero vibration, the vibrating body 110 must be supported only by the center PQ.

The present invention focuses on such a point, and an object of the present invention is to obtain a piezoelectric transformer that is easily supported and has high vibration efficiency.

[0007]

In order to achieve the above object, the present invention provides a set of input electrodes formed symmetrically with respect to an opposing surface of a vibrating body; A pair of output-side electrodes formed so as to be symmetrical with respect to the vibrating body; and providing the vibrating body in a direction parallel to the input-side electrode and the output-side electrode, on the input side and the output side. It is characterized by vibrating in a secondary vibration mode by polarization in a direction orthogonal to the direction.

According to another aspect of the invention, one of the input-side electrode and the output-side electrode is formed at a central portion of the vibrating body, and the other is formed at both end portions of the vibrating body. Further, an internal electrode for polarization is formed on at least one of the portions of the vibrating body sandwiched between the input side electrode and the output side electrode. The vibrating body is supported at nodes of vibration when free vibration occurs.

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

[0010]

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.

[0011]

First Embodiment First, a first embodiment will be described with reference to FIGS. FIG. 1A is a perspective view of the first embodiment. Also, a cross section viewed in the direction of the arrow along the line # 1B- # 1B in FIG.
The cross section viewed in the direction of the arrow along the line # 1C- # 1C is shown in FIG. FIG. 3D shows a cross section in the length direction of the quadrangular prism-shaped vibrating body. The input side (primary side) or the output side (secondary side) may be set according to the step-up or step-down, but in the following description, the left side of FIG. The right side is the output side.

First, the polarization direction of the vibrating body 10 will be described. As shown in FIGS.
Polarized in the thickness direction of the vibrating body 10 indicated by A. The output side is polarized in the length direction of the vibrating body 10 as shown by the arrow FB. These polarization directions are the same as in the Rosen type described above. However, in this embodiment, the electrode arrangement is different from that of the Rosen type. That is, the electrodes 12, 14, 16, 18 are formed symmetrically on both side surfaces 10A, 10B of the vibrating body 10. An AC voltage 20 for driving corresponding to the resonance frequency of the vibrating body is applied to the electrodes 12 and 14 on the input side. Also, the output side electrode 16,
From 18, an output voltage 22 is extracted.

Next, an example of a method of polarizing the vibrating body 10 will be described with reference to FIG. First, in the example shown in FIG. 1A, polarization electrodes 24 and 26 are provided on the upper and lower surfaces 10C and 10D of the vibrating body 10, respectively. Polarized in the direction of arrow FA. The right side 1 of the vibrating body 10
A polarization electrode 28 is provided at 0E. By applying a DC voltage between the polarization electrode 28 and the polarization electrodes 24 and 26, the right side of the vibrating body 10 is polarized in the direction of arrow FB. Such polarization electrodes 24 to 28 may be formed on the vibrating body 10 together with the input / output electrodes 12 to 18 shown in FIG.

Next, the example shown in FIG. 2B is another example of the polarization method on the input side, and FIG. 2C shows a cross section taken along line # 2- # 2 of FIG. Have been. As shown in these figures, a plurality of polarizing electrodes 30 are stacked inside the left side of the vibrating body 10, and these polarizing electrodes 30 are alternately connected to the electrodes 12, 14 on the side surfaces of the vibrating body. Electrode 1
By applying a DC voltage to the electrodes 2, 14,
The vibrating body 10 is polarized in the direction of the arrow FA which is the laminating direction of the vibrating member 10. Focusing on any one of the electrodes 30 for polarization, the directions of the electric field are reversed above and below the polarization electrode 30, so that the polarization directions are also reversed.

Next, the example shown in FIG. 2D is another example of the polarization method on the output side.
2 are laminated, and the polarization electrodes 32 are alternately connected to the electrodes 34 and 36 on the upper and lower surfaces of the vibrator, respectively. By applying a DC voltage to the electrodes 34 and 36,
The vibrating body 10 is polarized in the direction of the arrow FB, which is the direction in which the polarization electrodes 32 are stacked. Note that the point that the polarization directions are opposite on the left and right of one internal electrode 32 is the same as in FIG. 2B. In the example shown in FIG. 9E, the electrodes 16 and 18 shown in FIG. 1 are used in place of the polarizing electrodes 34 and 36 in the example shown in FIG. Electrode 32
Are alternately connected to the electrodes 16 and 18. By applying a DC voltage to these electrodes 16 and 18, FIG.
The same polarization as described above can be performed.

Next, the operation of this embodiment will be described. On the input side, when an AC voltage 20 having a resonance frequency of the vibrating body 10 is applied between the electrodes 12 and 14, the electromechanical coupling coefficient d31
This causes a longitudinal vibration in the direction of arrow FC, and the vibrating body 10 expands and contracts in the direction of arrow FD. These vibrations and expansions and contractions are caused by the vibrating body 1
When the vibration is transmitted to the output side of 0, the vibration of the vibrating body 10 occurs in the direction of arrow FE on the output side. Since the vibration direction FE is orthogonal to the polarization direction FB, the vibration body 10 expands and contracts in the direction of arrow FF, and the voltage 22 is generated by the electromechanical coupling coefficient g31. This voltage 22 is extracted from the electrodes 16, 18.

FIG. 3 shows how the vibrating body 10 vibrates. First, the example shown in FIG. 4A is a case where the total length of the vibrating body 10 is “1” and the vibrating body 10 is forcibly fixed at positions PA and PB of “0.25” from both ends. . The vibration amplitude in this case is as shown by a graph GA in FIG. On the other hand, FIG.
Vibrates with both ends as free ends, which is a so-called free vibration case. Positions PC and PD at "0.225" from both ends
The vibrating body 10 is fixed. The vibration amplitude in this case is as shown by a graph GB in FIG. In the case of FIG. 3A, a node, that is, a node point having zero amplitude, is forcibly formed in the vibrating body 10 at the positions PA and PB. On the other hand, in the case of FIG. 3C, since the vibrating body 10 is supported at the positions PC and PD, which are nodes of free vibration, the vibration is not hindered.

As described above, according to this embodiment, both the input side electrode and the output side electrode are formed on the side surface of the vibrator, and the input side has a coupling coefficient d31 and the output side has a coupling coefficient g31 in the secondary mode. Vibration occurs. Therefore, as compared with the Rosen type described above, there are two nodes of vibration, and it is possible to easily support the vibrating body. In addition, if a node of free vibration is supported, high vibration efficiency can be obtained because the vibration is not hindered.

When the adjustment of the vibration frequency or the oblique vibration mode is performed after the lead is attached or supported, the vibration
Is generally difficult to process. However, if the capacitance is adjusted by trimming the electrode for polarization which is not directly involved in the operation, such adjustment can be easily performed after the lead is attached.

[0020]

Second Embodiment Next, a second embodiment will be described with reference to FIG. In the embodiment described above, one of the vibrators in the length direction is an input unit, and the other is an output unit. However, in this embodiment, the central portion and both end portions of the vibrating body serve as input portions or output portions. (A) is a side view, (B) is a plan view, and (C) is a cross-sectional view in the length direction. In these figures, the electrodes 5 are provided on the side surfaces 50A and 50B of the vibrating body 50.
2, 54, 56, 58, 60 and 62 are formed symmetrically. Polarizing electrodes 64 and 66 are formed on the end surfaces 50C and 50D of the vibrating body 50. Further, the vibrating body 5
In the central part of 0, a polarization internal electrode 68 is formed by lamination.

Next, a method of polarizing the vibrating body 50 will be described. The central part of the vibrating body 50 is
Is applied in the direction of arrow FG. The left and right ends of the vibrating body 50 are provided with the electrodes 52 and 54 (or the polarization internal electrode 68) and the polarization electrodes 6 at both ends.
By applying a DC voltage between 4, F and 66, arrows FH,
Polarized in the FI direction.

Next, the operation will be described. When an AC voltage 70 corresponding to the resonance frequency of the vibrating body 50 is applied between the electrodes 52 and 54, a longitudinal vibration occurs in the direction of the arrow FG which is the polarization direction due to the electromechanical coupling coefficient d31, and the horizontal direction as the arrows FH and FI The vibrating body 50 expands and contracts in the direction. These vibrations and expansions and contractions are transmitted to both ends of the vibrating body 50. Since this vibration direction is orthogonal to the polarization directions FH and FI on the output side, a voltage is generated by the electromechanical coupling coefficient g31. Voltage 7
2 is taken from electrodes 56 and 58, and voltage 74 is applied to electrode 6
0,62.

According to this embodiment, on the input side, the vibrating body 50 is polarized in the direction of the arrow FG by the polarization internal electrode 68. Therefore, for example, the polarization can be easily performed as compared with the polarization method using the external electrodes shown in FIG. Also, on the output side, if the length of the vibrating body 50 is the same as in the above-described embodiment, the electrodes 52, 5
Since the distance from the electrode 4 (or the internal electrode 68 for polarization) to the electrodes 64 and 66 for polarization at both ends is reduced, the polarization can be easily performed in the same manner.

[0024]

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 present invention is applied to a prism-shaped vibrating body. However, the present invention can be applied to various vibrating body shapes such as a flat plate shape. (2) Which of the input side and the output side may be set from the relation of step-up and step-down.

[0025]

As described above, according to the present invention,
The input side electrode and the output side electrode are formed side by side symmetrically on the opposing surface of the vibrating body, and the vibration is performed in the secondary mode, so that the vibrating body can be easily supported, and in particular, free vibration can be performed. There is an effect that high vibration efficiency can be obtained by supporting the node.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention. (A) is a perspective view, (B) is a cross-sectional view taken along line # 1B- # 1B in (A), and (C) is an arrow along line # 1C- # 1C in (A). (D) is a sectional view in the longitudinal direction of the vibrating body.

FIG. 2 is a diagram illustrating a polarization method according to the first embodiment. (A),
(B), (D), (E) are cross-sectional views in the length direction of the vibrating body,
(C) is a sectional view taken along the line # 2- # 2 in (B) and viewed in the direction of the arrow.

FIG. 3 is a diagram illustrating a supporting method according to the first embodiment. (A),
(C) is a side view in the length direction of the vibrating body, and (B) is a waveform diagram showing the vibration amplitude.

FIG. 4 is a diagram showing a second embodiment. (A) is a side view,
(B), (C) is a sectional view along the length direction of the vibrating body.

FIG. 5 is a diagram illustrating an example of the configuration and amplitude of a Rosen-type piezoelectric transformer.

[Explanation of symbols]

10, 50: vibrating body 10A, 10B, 50A, 50B: side surface 10C, 10D: upper and lower surfaces 12, 14, 16, 18, 52, 54, 56, 58, 6
0,62 ... Electrode 20,70 ... AC voltage 22,72,74 ... Output voltage 24,26,28,30,32,34,36,64,6
6, 68: Electrode for polarization 30: Electrode for extraction 50C, 50D: End face FA, FB, FG, FH, FI: Polarization direction FC, FE: Vibration direction FD, FF: Expansion / contraction PA, PB, PC, PD: Support position

 ──────────────────────────────────────────────────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] 1. A set of input electrodes formed symmetrically with respect to a facing surface of a vibrating body; a set formed in parallel with these input electrodes and formed symmetrically with respect to the vibrating body. The vibrating body is polarized in a direction parallel to the input side electrode and the output side electrode and orthogonal to the input side and the output side to vibrate in the secondary vibration mode. A piezoelectric transformer characterized by the following. 2. The piezoelectric transformer according to claim 1, wherein one of the input side electrode and the output side electrode is formed at a central portion of the vibrating body, and the other is formed at both end portions of the vibrating body. 3. The piezoelectric transformer according to claim 1, wherein an internal electrode for polarization is formed on at least one of the portions of the vibrator sandwiched between the input side electrode and the output side electrode. 4. The piezoelectric transformer according to claim 1, wherein the vibrator is supported at a node of vibration when the vibrator is freely vibrated.