JPH10135531A - Piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the degree of freedom in setting the polarization direction on the input side and the output side of a vibration body and its supporting position. SOLUTION: The center of an oscillating body 22 is on the position shown by a one dot chain line LA in the state in which AC voltage is not applied. When AC voltage is applied to an input-side piezoelectric part 10, an oscillation part 12 is oscillated in vertical direction. This piezoelectric part 12 is coupled to the center part of the output-side piezoelectric body 22, and as both ends of the piezoelectric body 22 are formed free ends, the oscillation body 22 performs free oscillation in primary mode, and the center LA of the oscillation body 22 oscillates as shown by dotted lines LB and LC. This oscillation body 22 is supported by freely oscillating node points PA and PB. As the oscillation body is divided into an input side and an output side, polarization can be provided separately and an electrode can be formed separately.

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. Technical report US95-22, EMD95-18, CPM95-30 (1993-02), P17-21
(Publication Example 5) discloses a piezoelectric transformer for a cold cathode tube, which is driven at a voltage twice the power supply voltage using a full bridge circuit.

Focusing on the vibrating body, the known example 1 has a disk shape, the known examples 2 and 3 have a laminated shape, and the most basic Rosen type and the known examples 4 and 5 have a flat plate shape. In both cases, electrodes on the input side and the output side are formed on the integrated vibrating body. For this reason, the direction of polarization of the vibrating body is determined depending on how the vibrating body and the electrode are formed, and there is a disadvantage that the polarization direction cannot be set completely independently on the input side and the output side. In addition, since the positions of the electrodes and the like are determined assuming a predetermined vibration mode, it is not easy to change the vibration mode. Further, depending on the vibration mode, it is necessary to support the vibrating body at a position where the vibration of the vibrating body is hindered.

The present invention focuses on such a point, and an object of the present invention is to improve the selectivity of the setting of the polarization direction and the supporting position or the vibration mode on the input side and the output side of the vibrating body. is there. Another object is to improve the vibration efficiency of the vibrating body.

[0006]

In order to achieve the above-mentioned object, the present invention provides a first vibrating body in which an electrode for extracting an output voltage is formed on a vibrating body subjected to polarization; a vibrating body subjected to polarization An electrode for applying a voltage on the input side is formed on the first piezoelectric unit, and is configured independently of the first piezoelectric unit.
A second piezoelectric unit coupled to a position of a vibration antinode of the piezoelectric unit;
It is characterized by having.

According to another aspect of the present invention, the second piezoelectric section includes:
The first piezoelectric portions are symmetrically arranged with respect to the vibrator.
Further, a lead pattern for extracting an electrode is formed on the surface of the vibrating body of the first piezoelectric portion. Furthermore, the first
Both ends of the vibrating body of the piezoelectric portion are formed heavier than the central portion. The vibrating body of the first piezoelectric unit is supported at its free vibration node.

[0008] The above and other objects, features, and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

[0009]

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.

[0010]

Embodiment 1 First, Embodiment 1 will be described with reference to FIGS. FIG. 1A shows the appearance 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 external electrodes 14 and 16 formed on both left and right ends of a plate-shaped vibrating body 12, respectively, and further has a horizontal inside. A plurality of internal electrodes 15 (illustrated only in FIG. 1A) are formed along, that is, stacked in the thickness direction.
The internal electrodes 15 are alternately connected to the external electrodes 14 and 16, respectively. Then, by applying a DC voltage to the external electrodes 14 and 16, the vibrating body 12 is polarized in the direction of the arrow FA that is the laminating direction of the internal electrodes 15. Focusing on any one of the internal electrodes 15, since the directions of the electric fields are reversed above and below the internal electrodes 15, the polarization directions are also reversed.

Next, as shown in FIG. 1C, the output-side piezoelectric section 20 has a configuration in which external electrodes 24 and 26 are formed on the left and right ends of a plate-shaped vibrator 22, respectively. Then, by applying a DC voltage to these external electrodes 24 and 26, the vibrating body 22 is polarized in the direction of arrow FD. The input-side piezoelectric section 10 described above is coupled to the center of the upper surface of the output-side piezoelectric section 20 by an adhesive or the like as shown in FIG. FIG. 2 shows the side surface in the connected state.

Next, the operation of this embodiment will be described. When an AC voltage 18 having the resonance frequency of the vibrating body 12 is applied between the external electrodes 14 and 16 in the input-side piezoelectric section 10, longitudinal vibration occurs in the direction of arrow FB due to the electromechanical coupling coefficient d31.
The vibrating body 12 expands and contracts in the direction of arrow FC. These vibrations,
When the expansion and contraction is transmitted to the output side piezoelectric portion 20 through the connecting portion of the vibrating bodies 12 and 22, a longitudinal vibration of the vibrating body 22 occurs in the direction of arrow FE on the output side. Since the vibration direction FE is orthogonal to the polarization direction FD, the vibration body 22 expands and contracts in the direction of arrow FF, and the voltage 28
Is generated. This voltage 28 is extracted from the electrodes 24 and 26.

FIG. 2 shows a state of vibration of the vibrating body 22 in the output side piezoelectric section 20. In a state where the AC voltage 18 is not applied, the center of the vibrating body 22 is located at a position indicated by a chain line LA. Here, when an AC voltage 18 is applied to the input-side piezoelectric section 10, the vibrating body 12 vibrates in the vertical direction. On the other hand, the input-side vibrating body 12 is coupled to the central portion of the output-side vibrating body 22, and both ends of the output-side vibrating body 22 are free ends. Becomes That is, the vibrating body 22 vibrates as its center LA is indicated by the dotted lines LB and LC. Thus, in this embodiment, the vibrating body 22 freely vibrates.
Therefore, assuming that the total length is “1”, nodes of vibration, that is, node points PA and P of zero amplitude are located at positions “0.225” from both ends.
B exists. Therefore, the vibrating body 22 is supported at these positions PA and PB.

As described above, according to this embodiment, 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. Similarly, the positions of the electrodes can be separately and independently arranged, so that the wiring can be easily performed. Each of the vibrators is free vibration, and the vibration is not hindered by the support means, so that good vibration efficiency can be obtained.

[0016]

Second Embodiment Next, a second embodiment will be described with reference to FIG. First, the example shown in FIG. 2A shows another input-side piezoelectric unit 30 having the same configuration as the input-side piezoelectric unit 10 described above.
Are provided symmetrically with the input-side piezoelectric unit 10 with the output-side piezoelectric unit 20 interposed therebetween. The vibrators 12, 32 of the input-side piezoelectric units 10, 30 are driven to vibrate in the same direction. That is, if the vibrating body 12 vibrates upward in the figure, the vibrating body 32 also vibrates upward in the figure, and if the vibrating body 12 vibrates downward in the figure, the vibrating body 32 also vibrates downward in the figure. The phases of the AC voltages 18, 38 are adjusted so that such vibrations in the same direction are obtained. Note that whether or not the AC voltages 18 and 38 have the same phase is determined by the vibrating body 1
It depends on 2, 32 polarization directions.

With the above configuration, the free vibration shown by the dotted lines LB and LC in FIG.
With 0 and 30, the efficiency is doubled, the amplitude is increased and a high boost ratio can be obtained.

Next, the embodiment shown in FIG. 3B is an example in which the positions of the input side piezoelectric units 10 and 30 are changed so that the output side piezoelectric unit 20 is vibrated in the secondary mode. The amplitude change in the case of the free vibration of the second mode is as shown in FIG.
C, PD, and PE exist. The input-side piezoelectric units 10 and 30 are arranged at the antinodes of the vibration. In addition,
Although the input-side piezoelectric units 10 and 30 are provided on the front and back of the output-side piezoelectric unit 20, respectively, it is a matter of course that both may be provided on the same surface.

In this example, the vibrating bodies 12, 32 of the input-side piezoelectric units 10, 30 are driven so as to vibrate in opposite directions. That is, if the vibrating body 12 vibrates upward in the figure, the vibrating body 32 vibrates downward in the figure, and if the vibrating body 12 vibrates downward in the figure, the vibrating body 32 vibrates upward in the figure. Compared with the case of FIG.
The phases of 38 may be just reversed.

As is clear from the comparison between the example shown in FIG. 2A and the example shown in FIG. 2B, only by changing the position of the input side piezoelectric units 10 and 30 to adjust the vibration phase, the primary mode and the secondary mode can be obtained. In any of the following modes, the vibration mode can be easily obtained. Of course, third and higher order vibration modes are also possible. If such a higher mode is used, a transformer driven in a high frequency band can be easily realized. The point that the vibrating body 22 is supported at the node points PC, PD, and PE is the same as in the above-described embodiment.

Next, the example shown in FIG. 3D is a further improvement in the efficiency of the example of the secondary mode shown in FIG. That is, the other input-side piezoelectric units 40 and 50 having the same configuration as the above-described input-side piezoelectric unit 10 are provided symmetrically with the input-side piezoelectric units 10 and 30 with the output-side piezoelectric unit 20 interposed therebetween. The vibrators 12, 42 of the input-side piezoelectric units 10, 40 are driven to vibrate in the same direction. That is, the vibrating body 12
Is vibrated upward in the figure, the vibrating body 42 also vibrates upward in the figure, and if the vibrating body 12 vibrates downward in the figure, the vibrating body 42 also vibrates downward in the figure. Similarly, the vibrators 32, 52 of the input-side piezoelectric units 30, 50 are driven to vibrate in the same direction. That is, if the vibrating body 32 vibrates upward in the figure, the vibrating body 52 also vibrates upward in the figure, and if the vibrating body 32 vibrates downward in the figure, the vibrating body 52 also vibrates downward in the figure.

Further, a set of the vibrating bodies 10 and 40 and the vibrating body 3
The set of 0,50 is driven to oscillate in the opposite direction. That is, if the vibrators 12, 42 vibrate upward in the figure, the vibrators 32, 52 vibrate downward in the figure, and the vibrators 12, 42
If 42 vibrates downward in the figure, the vibrators 32 and 52 vibrate upward in the figure. In this example, the secondary vibration shown in FIG. 7C is performed with a larger amplitude, and the boost ratio can be improved as in the example of FIG.

[0023]

Third Embodiment Next, a third embodiment will be described with reference to FIG. First, in the example shown in FIG. 1A, the electrode lead is devised. As described above, since the vibrating body has free vibration on both the input side and the output side,
The external electrode is at a site that vibrates to some extent. However, in order to avoid disconnection due to vibration and alienation of the vibration, it is convenient to lead the lead wire to the outside from a place not vibrating. Therefore, in the present embodiment, a lead pattern is formed up to a node point which is a node of vibration, and is drawn out from this.

In FIG. 2A, the external electrode 14 of the input-side piezoelectric section 10 is guided near the node point PA by a lead pattern 60 extending from the surface 22A of the vibrating body 22 of the output-side piezoelectric section 20 to the side surface 22B. I have. Position side piezoelectric unit 10
Similarly, the other external electrode 16 also has a surface 22
It is guided near the node point PA by the lead pattern 62 from A to the side surface 22B. On the other hand, the output side piezoelectric unit 2
The zero external electrodes 24 and 26 are guided to the vicinity of the node point PA by the lead patterns 64 and 66 on the side surface 22B of the vibrating body 22.

Using such a lead pattern,
The input / output lead wires are concentrated near the node point PA, disconnection due to vibration is reduced, reliability is improved, alienation of vibration can be reduced, and efficiency is further improved. The external electrodes 14 and 16 of the input-side piezoelectric section 10 and the lead patterns 60 and 62
If necessary, further disconnection can be prevented by using a twisted wire and soldering them together, or connecting them at a plurality of locations as shown by dotted lines 60A and 60B. it can.

Next, the example shown in FIG. 2B is an example in which the vibrating body 72 of the output-side piezoelectric section 70 is made heavier at both ends than at the center where the input-side piezoelectric section 10 is mounted. In the illustrated example, when viewed from the side, both ends of the vibrating body 72 are spread in a horn shape, and external electrodes 74 and 76 are formed at the ends. The supporting is performed at the node of the vibration of the vibrating body 72 as in the above embodiment. According to this example, since both ends of the vibrating body 72 are heavy, the amplitude with respect to the vertical vibration increases, and a large boosting ratio can be obtained.

[0027]

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. Similarly, the shape and arrangement of the electrodes of the vibrating body, and the directions of polarization and vibration may be appropriately set as necessary.

(2) In the above embodiment, the input side piezoelectric portion has a laminated structure, but this is to facilitate the polarization of the vibrating body and to increase the boost ratio, which prevents a single layer structure. Not something. Conversely, the output side piezoelectric section may have a laminated structure.

[0029]

As described above, according to the present invention,
Since the input side and output side piezoelectric parts are separately configured and coupled, the range of setting of the polarization direction and the selection of the support position on the input side and the output side are widened, and the design flexibility is improved. In addition to this, there is an effect that various vibration modes can be easily handled.

[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 sectional view on the input side, and (C) is a sectional view on the output side.

FIG. 2 is a front view showing a vibration state of the first embodiment.

FIG. 3 is a diagram showing a second embodiment. (A), (B),
(D) is a front view, and (C) is a graph showing vibration amplitude.

FIG. 4 is a perspective view showing a third embodiment.

[Explanation of symbols]

10, 30, 40, 50 ... input side piezoelectric part 20, 70 ... output side piezoelectric part 12, 22, 32, 42, 52, 72 ... vibrating body 14, 16, 24, 26 ... external electrode 15 ... internal electrode 18, 38 AC voltage 28 Output voltage 60, 60A, 60B, 62, 64, 66 Lead pattern FA, FD Polarization direction FB, FE Vibration direction FC, FF Expansion / contraction LA LA Center of vibration body at rest LB , LC: Center of the vibrating body during vibration PA, PB, PC, PD, PE: Node point

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

Claims (5)

[Claims] A first piezoelectric portion having an electrode for extracting an output voltage formed on a polarized vibrating body; an electrode for applying an input-side voltage to the polarized vibrating body;
A second piezoelectric unit configured independently of the first piezoelectric unit and coupled to a vibration antinode of the first piezoelectric unit; 2. The piezoelectric transformer according to claim 1, wherein the second piezoelectric section is symmetrically arranged with the vibrator of the first piezoelectric section interposed therebetween. 3. The piezoelectric transformer according to claim 1, wherein a lead pattern for extracting an electrode is formed on a surface of the vibrating body of the first piezoelectric unit. 4. The piezoelectric transformer according to claim 1, wherein both ends of the vibrating body of the first piezoelectric portion are formed heavier than a central portion. 5. The vibrating body of the first piezoelectric unit is supported at a free vibration node point.
The piezoelectric transformer according to 2, 3, or 4.