JPH114026A - Laminated-type piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a safe piezoelectric transformer, provided with high conversion efficiency for easily matched impedance and separating input and output by turning a drive part and a power generation part into constitution such that a piezoelectric body and an internal electrode are alternately laminated and an insulation part is provided between them in a laminated (step-down) type piezoelectric transformer. SOLUTION: In a laminated (step-down)-type piezoelectric transformer element composed of a drive part 11 and the power generation part 12 for which a piezoelectric body 111 polarized in a thickness direction and internal electrodes 112, 113, 118 and 119 are laminated for a plurality of on-both end sides of the length direction of the piezoelectric body in a long plate shape and external electrodes 114, 116, 120 and 122, the thickness of the piezoelectric body 111 of the drive part 11 is made larger than the thickness of the piezoelectric body 111 of the power generation part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer used for various types of DC power supplies, and more particularly to a stacked step-down type or a transformer suitable for use in a small rectified power supply requiring miniaturization, weight reduction and high reliability. The present invention relates to a step-up type piezoelectric transformer.

[0002]

2. Description of the Related Art Conventionally, a winding type electromagnetic transformer has been used as a step-down type transformer of an AC adapter for supplying power from a commercial power supply line to various battery-driven electronic devices. This electromagnetic transformer has a structure in which a conductive wire is wound around a magnetic core, and it has been very difficult to realize a small and lightweight electromagnetic transformer.

On the other hand, a piezoelectric transformer whose operation principle is completely different from that of an electromagnetic transformer is disclosed in R. A. ROS
EN (US Patent 2,830,
274). FIG. 2 shows a typical example of this structure (the piezoelectric transformer is driven in the λ / 2 mode).

Referring to FIG. 2, a portion in which planar electrodes 202 and 203 are provided on the upper and lower surfaces of a piezoelectric body 201 is a driving unit 21.
And polarized in the thickness direction. The portion sandwiched between the end face electrode 204 provided at the end of the piezoelectric body 201 and the drive section 21 is the power generation section 22 which is polarized in the length direction.

In this piezoelectric transformer, a support 205 is attached to a node at the time of longitudinal vibration resonance in the longitudinal direction, and is fixed to a support (not shown). In this state, the planar electrodes 202, 2
When an AC voltage having a resonance frequency of longitudinal vibration in the longitudinal direction of the piezoelectric body 201 is applied via the external electric terminals 206 and 207 connected to the external electric terminal 203 and the external electric terminal 208 connected to the end face electrode 204, And a voltage is generated.

However, the piezoelectric transformer shown in FIG. 2 has a problem that the efficiency and reliability are reduced because the connection positions of the external electric terminals are not nodes of vibration in both the driving section and the power generation section. Further, since the piezoelectric transformer is a single plate, there is a problem that the boosting ratio cannot be sufficiently increased.

As a conventional technique intended to improve these problems, for example, a laminated piezoelectric transformer proposed in Japanese Patent Application Laid-Open No. Hei 6-224484 is known.
FIG. 3 is a cross-sectional view showing the configuration of this conventional laminated piezoelectric transformer. This multilayer piezoelectric transformer is driven at a drive frequency in a triple mode of λ / 2.

Referring to FIG. 3, in the laminated piezoelectric transformer, a portion indicated by reference numeral 31 in the rectangular piezoelectric plate 310 is a low-impedance driving section, and planar internal electrodes 311 and 312 and a piezoelectric body 313 are provided. Are alternately laminated, and planar electrodes 314 and 315 are provided on upper and lower surfaces, and external electrodes (not shown) are formed on side surfaces for connection of internal electrodes. These portions are polarized in the thickness direction.

Similarly, a portion indicated by 32 is a high-impedance power generation section, in which a plurality of strip-shaped internal electrodes 317 and piezoelectric bodies 313 are alternately laminated, and strip-shaped electrodes 318 and 319 are formed on upper and lower surfaces. An external electrode (not shown) is provided on the side surface for connecting the internal electrode.

The power generation section is polarized in the length direction. Since this piezoelectric transformer can connect the external electric terminals 321, 322 and 323 at the nodes of the longitudinal vibration in the longitudinal direction, the efficiency and reliability do not decrease as described above. The boost ratio can be increased.

By the way, the above-mentioned piezoelectric transformers are all of the step-up type, and when these inputs and outputs are reversed and used for the step-down type, there are problems of impedance matching, conversion efficiency, etc. is not.

On the other hand, a step-down type piezoelectric transformer is disclosed in Japanese Patent Application Laid-Open Nos. 8-153914 and 6-177.
451 and JP-A-5-235432.

First, FIG. 4 shows the configuration of a step-down type piezoelectric transformer proposed in the above-mentioned Japanese Patent Application Laid-Open No. 8-153914. In FIG. 4, a portion indicated by reference numeral 41 is a drive unit, and internal electrodes 401 and 402 and piezoelectric bodies 403 are alternately laminated in a plurality of layers, and each internal electrode is electrically connected via an external electric terminal (not shown). Have been. And these parts are
Polarized in the thickness direction.

A portion indicated by reference numeral 42 is a power generation portion, in which a plurality of layers of internal electrodes 406 and 407 and a piezoelectric body 408 are alternately laminated, and each internal electrode is electrically connected via an external electric terminal (not shown). It is connected. This piezoelectric transformer generates vibration in the length direction of the power generation unit in conjunction with vibration in the length direction of the drive unit, and generates a stepped-down voltage.
An AC voltage having a primary resonance frequency in the longitudinal direction is applied to the drive unit 41 via the external electric terminals 404 and 405, and the voltage stepped down to the power generation unit 42 via the external electric terminals 409 and 410. What happens.

FIG. 5 shows a configuration of a step-down type piezoelectric transformer proposed in the above-mentioned Japanese Patent Application Laid-Open No. 6-177451. In FIG. 5, a portion indicated by 51 is a power generation unit,
Flat electrodes 501 and 502 are provided on the upper and lower surfaces in the longitudinal direction,
Polarized in the thickness direction. Further, a portion indicated by 52 is a driving portion, and an input electrode 503 is provided on a side surface in the length direction,
Polarized in the width direction between the planar electrodes 501 and 502 of the driving unit. This piezoelectric transformer utilizes the longitudinal vibration lateral effect, applies an AC voltage having a primary resonance frequency in the longitudinal direction via external electric terminals 504 and 505, and applies the AC voltage via external electric terminals 505 and 506. , And generates a stepped-down voltage in the power generation unit 51.

Finally, the configuration of the step-down type piezoelectric transformer proposed in Japanese Patent Laid-Open No. 5-235432 is shown in FIG.
Shown in In FIG. 6, a portion indicated by reference numeral 61 is a driving portion, and the internal electrodes 601 and 602 and the piezoelectric body 603 are laminated.
Each internal electrode is electrically connected via an external electric terminal (not shown). These portions are polarized in the thickness direction.

A portion indicated by reference numeral 62 is a power generation portion, in which a plurality of layers of the internal electrodes 606 and 607 and the piezoelectric body 608 are alternately laminated, and each of the internal electrodes is electrically connected via an external electric terminal (not shown). It is connected. These portions are also polarized in the thickness direction. This piezoelectric transformer generates vibration in the thickness direction of the power generation unit in conjunction with vertical vibration in the thickness direction of the drive unit, and generates a stepped-down voltage.
An AC voltage having a tertiary resonance frequency in the thickness direction is applied to the drive unit 61 via the external electric terminals 604 and 605, and the stepped-down voltage is applied to the power generation unit 62 via the external electric terminals 609 and 610. What happens.

[0018]

However, each of the above-mentioned prior arts has the following problems.

(1) As a first problem, the conventional ROS
EN type piezoelectric transformer (US Pat. No. 2,830,274)
Each of the piezoelectric transformers proposed in JP-A-6-224484 is a step-up type, and if the input and output are reversed, it becomes a step-down type in principle. However, there is a problem in conversion efficiency, which is not practical.

(2) As a second problem, among the step-down type piezoelectric transformers, the piezoelectric transformer proposed in Japanese Patent Application Laid-Open No. 8-153914 is described.
The vibration in the length direction of the power generation unit is generated in conjunction with the vibration in the length direction of the driving unit, and a primary vibration mode in the length direction is used. For this reason, it is difficult to hold the piezoelectric transformer at the node of the vibration, and there is a problem that the conversion efficiency cannot be sufficiently increased.

(3) As a third problem, Japanese Patent Laid-Open No.
The piezoelectric transformer proposed in Japanese Patent Application Laid-Open No. 177451 will be described. The piezoelectric transformer uses a longitudinal vibration transverse effect, is a single-plate type, and has a common input / output ground. For this reason, variations in impedance matching with the load are difficult to obtain, and there is also a safety problem due to the common ground of input and output.

(4) As a fourth problem, Japanese Patent Laid-Open No.
The piezoelectric transformer proposed in Japanese Patent Publication No. 235432 will be described. The piezoelectric transformer utilizes thickness longitudinal vibration. The driving frequency is too high at 2.4 MHz. There is a problem.

Accordingly, the present invention has been made in order to solve the above-mentioned conventional problems. By adopting a configuration in which the piezoelectric transformer is held at the node point, the conversion efficiency can be sufficiently increased, and the laminated layers can be formed. It is an object of the present invention to provide a laminated (step-down or step-up) type piezoelectric transformer which can easily achieve impedance matching with a configuration and has a configuration in which a driving unit and a power generation unit are separated, and has no problem in safety.

[0024]

In order to achieve the above object, a laminated piezoelectric transformer according to a first aspect of the present invention is provided on both ends of a long plate-shaped piezoelectric transformer in the length direction, and is polarized in a thickness direction. In the piezoelectric transformer in which the driving unit and the power generation unit in which the piezoelectric bodies and the internal electrodes are alternately stacked are arranged, and the insulating unit is arranged in a portion sandwiched between the driving unit and the power generation unit, the piezoelectric unit of the driving unit The thickness of one layer is greater than the thickness of one layer of the piezoelectric body of the power generation unit.

According to a second aspect of the present invention, there is provided a laminated piezoelectric transformer according to the first aspect, wherein the driving section and the power generation section are each provided with a mechanical resonance of longitudinal vibration in a longitudinal direction of the long plate-shaped piezoelectric transformer. Are separated from each other at a position １ ／ of the wavelength λ, and driven in a vibration mode twice as large as １ ／ of the wavelength λ.

Further, the present invention provides, as a third viewpoint, not only a step-down type but also a step-up (fourth viewpoint) laminated piezoelectric transformer.

As a fifth viewpoint, the laminated piezoelectric transformer according to the comprehensive viewpoint of the present invention is such that a piezoelectric body polarized in the thickness direction and an internal electrode are alternately provided at both ends in the length direction of the long plate-shaped piezoelectric transformer. Arrange the drive unit and power generation unit laminated on
In the piezoelectric transformer in which an insulating portion is disposed at a portion sandwiched between the driving portion and the power generation portion, a thickness of a piezoelectric body of the driving portion is different from a thickness of a piezoelectric body of the power generation portion. It is characterized by the following.

In the laminated piezoelectric transformer according to a fifth aspect of the present invention, in the sixth aspect, the drive unit and the power generation unit may be configured such that the driving unit and the power generation unit are configured to generate mechanical resonance of longitudinal vibration in a longitudinal direction of the long plate-shaped piezoelectric transformer. It is arranged separately at the position of the wavelength λ / 2, and is driven in a vibration mode twice the wavelength λ / 2.

[0029]

Embodiments of the present invention will be described below. In a preferred embodiment of the laminated piezoelectric transformer of the present invention, a driving section in which piezoelectric bodies polarized in the thickness direction and internal electrodes are alternately laminated on both ends in the length direction of the long plate-shaped piezoelectric transformer. (11 in FIG. 1) and a power generation unit (12 in FIG. 1) are disposed, and an insulating unit (13 in FIG. 1) is disposed between the drive unit and the power generation unit. The thickness of one layer of the piezoelectric body in 11) of FIG. 1 is larger than the thickness of one layer of the piezoelectric body of the power generation unit.

Then, in the embodiment of the present invention,
The drive unit and the power generation unit are separately arranged at a position of a wavelength の λ of mechanical resonance of longitudinal vibration in a longitudinal direction of the long plate-shaped piezoelectric transformer, and are driven in a vibration mode twice the wavelength λλ. I do.

The operation of the embodiment of the present invention will be described. As described above, in the present invention, each of the two ends of the long plate-shaped piezoelectric transformer is used as a drive unit and a power generation unit.
A configuration in which a plurality of layers of the internal electrode and the piezoelectric body are laminated, a driving unit,
An insulating section is provided at the boundary of the power generation section, and two sections in the length direction are further provided.
It is driven in the next mode.By changing the lamination structure, it is easy to reduce the impedance according to the impedance of the load, and since the driving unit and the power generation unit are insulated and separated, safety is ensured. There is no problem in point. Further, since the holding of the piezoelectric transformer can be performed at the node of the vibration, there is an operational effect that the conversion efficiency can be increased.

[0032]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

FIG. 1 is a perspective view showing the structure of the first embodiment of the present invention. Referring to FIG. 1, a portion indicated by reference numeral 11 is a high impedance driving portion of a piezoelectric transformer, and a piezoelectric body 11 is provided.
1 and a plurality of internal electrodes 112 and 113 are alternately laminated, and external electrodes formed on upper and lower surfaces are provided. In FIG. 1, only the external electrode 114 on the upper surface is shown, and the opposite side is shown. The external electrodes provided on the lower surface of are not shown.

Further, external electrodes 116 provided on the side portions,
External electrodes (not shown) provided on the side opposite to the side are external electrodes for electrically connecting the internal electrodes 112 and 113 exposed on the side surfaces facing each other. is there. The space between these electrodes is polarized in the thickness direction.

A portion indicated by reference numeral 12 is a low-impedance power generation unit, and includes a piezoelectric body 111 and internal electrodes 118 and 11.
9 are alternately laminated and provided with external electrodes formed on the upper and lower surfaces. In FIG.
Only 0 is shown, and the external electrodes provided on the opposite lower surface are not shown.

Also, external electrodes 122 provided on the side portions,
External electrodes (not shown) provided on the side opposite to the side are external electrodes for electrically connecting the internal electrodes 118 and 119 exposed on the side surfaces facing each other. is there. The space between these electrodes is polarized in the thickness direction.

An insulating section 13 is formed between the driving section 11 and the power generation section 12.

When the piezoelectric transformer of this embodiment is driven by inputting an AC voltage between the external electric terminals 124 and 125 connected to the electrodes of the drive unit 11, the external electric terminals 126 connected to the electrodes of the power generation unit 12 are driven. Voltage is output during the period 127.

Next, a method of manufacturing the piezoelectric transformer according to this embodiment will be described.

In the present embodiment, the piezoelectric transformer
Were manufactured by the green sheet method. The material of the piezoelectric body 111 was Nepec 8 (manufactured by Tokin).

The internal electrodes 112, 113, 118,
119 is a firing type Ag / Pd paste (Ag / Pd
Is 70/30 by weight, and the piezoelectric body 111 is used.
Is screen-printed in a predetermined pattern on a green sheet, and then laminated, and together with the piezoelectric body 111 at a temperature of 1200
It was formed by firing integrally under the conditions of ° C., keep time, 2 hours.

In this embodiment, PZT-based piezoelectric ceramics and Ag / Pd are used as the materials of the piezoelectric body and the internal electrodes. However, other combinations of piezoelectric materials having piezoelectricity and electrode materials which can be fired integrally therewith are used. Needless to say, it works.

As for the lamination structure, the driving section 11 has 7 piezoelectric layers and 6 internal electrodes, and the thickness between the internal electrodes is 285 μm.
And the internal electrodes are 34 layers, and the thickness between the internal electrodes is 57 μm.

Next, after firing, the length is 48 mm and the width is 15 m.
m, processed to a thickness of 2 mm and fired Ag / P
d paste is applied to the upper and lower surfaces and side surfaces of the drive unit 11 and the power generation unit 1.
2 After printing at predetermined positions on the upper and lower surfaces and side surfaces,
By firing at ℃, keep time 15 minutes,
External electrodes 114, 115, 116, 117, 120, 1
21, 122 and 123 were formed.

Next, using a polarization jig, a temperature of 100 to 2
In silicone oil at 00 ° C, an electric field of 2-3k
By applying V / mm, the drive unit 11 and the power generation unit 12 were each polarized.

A voltage was applied to the obtained piezoelectric transformer with a load of 10 Ω at a driving frequency of 70 kHz, and the piezoelectric transformer was driven in a secondary mode of resonance in the longitudinal direction to evaluate the transformer characteristics. The output power was 20 to 30 W And the conversion efficiency is 9
8.5% and a metamorphic ratio was 0.252.

On the other hand, in the conventional example (based on JP-A-6-177,451) as shown in FIG. 5 of the present application, the output power is 16 to 32 W, the conversion efficiency is 91 to 95%, and the transformation ratio is 0. 16 to 0.15.

As a result, it is understood that the piezoelectric transformer of this embodiment has a higher conversion efficiency than the conventional one.

Further, in the case of the present embodiment, the metamorphic ratio can be set in any manner by adjusting the lamination structure of the drive section and the power generation section regardless of the step-down or step-up. For this reason, it is meaningless to compare with the prior art.

Next, a second embodiment of the present invention will be described. The second embodiment of the present invention is different from the first embodiment in that the driving unit and the power generation unit of the piezoelectric transformer have a laminated structure and external dimensions. Therefore, only this point will be described.

The piezoelectric transformer according to the second embodiment of the present invention
As the laminated structure, the driving unit 11 has eight piezoelectric layers,
The internal electrodes have seven layers, and the thickness between the internal electrodes is 500 μm.
There are seven layers, and the thickness between the internal electrodes is 83 μm.

The external dimensions are 48 mm in length and 1 in width.
5 mm, thickness 4 mm.

A voltage was applied to the obtained piezoelectric transformer at a driving frequency of 70 kHz with a load of 10 Ω, and the piezoelectric transformer was driven in a secondary mode of longitudinal resonance. The transformer characteristics were evaluated. The output power was 30 to 40 W. And the conversion efficiency is 9
The transformation ratio was 8.3% and the conversion ratio was 0.167.

By making the laminated structure of the drive section and the power generation section different from that of the first embodiment, the conversion efficiency was not changed and the conversion ratio could be reduced. From this result,
By adjusting the lamination structure, the transformation ratio can be adjusted with high efficiency.

Although the first and second embodiments have been described with respect to the step-down type, the present invention can be similarly implemented even if the step-up type is realized by reversing the relationship between the input and output. It has.

[0056]

As described above, according to the present invention, the driving section and the power generation section are configured by alternately stacking a plurality of piezoelectric bodies and internal electrodes, and the insulating section is provided between the driving section and the power generation section. By driving in the secondary mode of resonance in the longitudinal direction, the piezoelectric transformer can be held at the node point, the conversion efficiency can be sufficiently increased, and the impedance is realized by the stacked configuration of the driving unit and the power generation unit. The effect is that matching can be easily achieved and the metamorphic ratio can be freely adjusted.

Further, according to the present invention, the input and output are separated from each other, so that there is no safety problem.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of a multilayer piezoelectric transformer according to one embodiment of the present invention.

FIG. 2 is a perspective view showing a configuration of a conventional single-plate type piezoelectric transformer.

FIG. 3 is a cross-sectional view illustrating a configuration of a conventional multilayer piezoelectric transformer.

FIG. 4 is a cross-sectional view showing a conventional step-down piezoelectric transformer.

FIG. 5 is a perspective view showing a conventional step-down piezoelectric transformer.

FIG. 6 is a perspective view showing a conventional step-down piezoelectric transformer.

[Explanation of symbols]

11, 21, 31, 41, 51, 61 Driving unit 12, 22, 32, 42, 52, 62 Power generating unit 13 Insulating unit 111, 201, 313, 403, 408, 603, 6
08 piezoelectric body 310 piezoelectric board 112, 113, 118, 119, 311, 312, 4
01, 402, 406, 407, 601, 602, 60
6, 607 Internal electrode 114, 115, 120, 121 External electrode 116, 117, 122, 123, 316, 320 External electrode (for connecting internal electrode) 202, 203, 314, 315, 501, 502 Planar electrode 204 End face electrode 205 Supporting tool 317 Strip-shaped internal electrode 318, 319 Strip-shaped electrode 503 Input electrode 124, 125, 126, 127, 206, 207, 2
08, 321, 322, 323, 404, 405, 40
9, 410, 504, 505, 506, 604, 60
5,609,610 External electric terminal

Claims (6)

[Claims] 1. A drive section and a power generation section in which piezoelectric bodies and internal electrodes polarized in a thickness direction are alternately laminated on both ends in a length direction of a long plate-shaped piezoelectric transformer. In a piezoelectric transformer in which an insulating portion is arranged at a portion sandwiched between the power generation units, a thickness of a piezoelectric body of the driving unit is larger than a thickness of a piezoelectric body of the power generation unit. Multilayer piezoelectric transformer. 2. The multilayer piezoelectric transformer according to claim 1, wherein the driving unit and the power generating unit are located at a position at a half of a wavelength λ of mechanical resonance of longitudinal vibration in a longitudinal direction of the long plate-shaped piezoelectric transformer. Wherein the piezoelectric transformer is driven in a vibration mode of twice the wavelength λ. 3. A multi-layer piezoelectric transformer according to claim 1, wherein the multi-layer piezoelectric transformer is used as a step-down transformer. 4. A drive section and a power generation section in which piezoelectric bodies polarized in the thickness direction and internal electrodes are alternately laminated on both ends in the length direction of the long plate-shaped piezoelectric transformer; In a piezoelectric transformer in which an insulating portion is arranged at a portion sandwiched between the power generation units, a thickness of one layer of the piezoelectric body of the driving unit is different from a thickness of one layer of the piezoelectric body of the power generation unit. Laminated piezoelectric transformer. 5. The laminated piezoelectric transformer according to claim 4, wherein the driving unit and the power generation unit are separated at a position of a wavelength λ / 2 of a mechanical resonance of a longitudinal vibration in a longitudinal direction of the long plate-shaped piezoelectric transformer. Characterized in that the piezoelectric transformer is driven in a vibration mode twice the wavelength λ / 2. 6. A multi-layer piezoelectric transformer according to claim 4 or 5, wherein the multi-layer piezoelectric transformer is used as a step-up transformer.