JPH0992901A - Piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high reliability and high step-up ratio. SOLUTION: A piezoelectric transformer uses the resonance mode in the longitudinal direction of a piezoelectric ceramic rectangular plate 11, which has surface electrodes 12a, 12b, and belt-like electrodes 13a, 13b, 14a, 14b, 15a, 15b, and is polarized in the direction of thickness between the surface electrodes 12a-12b. The surface electrodes have centers at 1/6 positions from one end in the length direction, and a nearly 1/3 length, and face each other in the thickness direction. The belt-like electrodes are perpendicular to the longitudinal direction at the positions 1/2, 1/3, 1/6 from the other end, and face each other in the direction of thickness. In the directions from the belt-like electrodes 13a, 13b to 14a-14b, from 15a, 15b to 14a, 14b, or from 14a, 14b to 13a, 13b, and from 14a, 14b to 15a, 15b, polarization is induced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer using a piezoelectric ceramic, and more particularly to a piezoelectric transformer utilizing resonance in the length direction of a piezoelectric ceramic rectangular plate.

[0002]

2. Description of the Related Art A static electricity generator, a device for lighting a backlight of a liquid crystal display and the like do not require a large current value, but use a high voltage power source of about 1 kV to several watts.

At present, electromagnetic transformers are used for boosting these power sources, but due to demands for reduction of generated electromagnetic noise, low power consumption, small size and low profile of equipment, etc.
The practical application of the piezoelectric transformer is being studied.

FIG. 3 is a perspective view schematically showing the structure of a piezoelectric vibrator used in a conventional 3λ / 2 mode piezoelectric transformer.

In FIG. 3, a piezoelectric ceramic rectangular plate 31 is provided.
The surface electrodes 32a, 32b of about ⅓ of the rectangular plate length, which are opposed to each other in the thickness direction, are formed on one side of the rectangular plate length direction from one end in the rectangular plate length direction at a center. There is.

Further, from the other end, the length of the rectangular plate is 1/3, 1
Strip-shaped electrodes 33a, 33b, 34a, 34b are formed at a position of / 6 to face each other in the thickness direction orthogonal to the length direction of the rectangular plate.

The piezoelectric ceramic rectangular plate 31 is used for the surface electrode 3
2a-32b is polarized in the thickness direction (arrow 35a),
Also, the surface electrodes 32a, 32b to the strip electrodes 33a, 33
b and the strip electrodes 34a, 34b to the strip electrodes 33a, 3
3b is polarized in the longitudinal direction (arrows 35b,
35c).

FIG. 2 is an explanatory view of the operation principle of a piezoelectric transformer vibrating in a 3/2 wavelength resonance mode of longitudinal vibration, and FIG. 2 (a) is a side view of a piezoelectric ceramic rectangular plate.
FIG. 2B is a diagram showing a displacement distribution when the piezoelectric ceramic rectangular plate is vibrating in a 3/2 wavelength resonance mode of longitudinal vibration, and FIG. 2C is a diagram showing a strain distribution. is there.

In FIG. 3, the input side terminal 36b is connected to GND.
As a terminal, when a voltage equal to the resonance frequency of the 3/2 wavelength resonance mode in the length direction of the piezoelectric ceramic rectangular plate is applied between the input-side terminals 36a-36b, the piezoelectric ceramic rectangular plate is connected to the piezoelectric ceramic rectangular plate shown in FIGS. It vibrates as shown in (c).

At this time, a voltage due to the piezoelectric effect is generated between the output side terminals 37a-37b. Here, the input side terminal 36
The capacitance between a-36b is the output side terminals 37a-37b.
It is a sufficiently large value as compared with the capacitance between them. Therefore, when a low voltage is applied to the input side to vibrate, a large voltage proportional to the ratio of the capacitance on the input side to the capacitance on the output side is generated on the output side.

[0011]

In response to the demand for lower voltage drive of static electricity generators, battery drive devices for liquid crystal backlights, etc., there is a possibility that they are in opposite phase to each other as proposed in Japanese Patent Application No. 6-180329. By using a full bridge circuit that supplies two pulse voltages to the input side terminals,
There is a driving method in which the input voltage is doubled and therefore the output voltage is also doubled.

In order to use this full bridge circuit, two terminals are required for each of the input side and the output side.

However, in the conventional 3λ / 2 mode piezoelectric transformer, since the input side and the output side have one terminal in common, this full bridge circuit cannot be used.

As one of means for solving this, as shown in FIG. 4, there is a piezoelectric transformer in which one electrode on the input side is divided into two parts, one of which is connected to the input side terminal 47a and the other of which is connected to the output side terminal 48a. However, since the capacitance on the input side becomes small, the boosting ratio becomes low. Further, the terminal cannot be taken out from the node point (the position where the displacement during vibration is 0), and the terminal is disconnected during the driving of the piezoelectric transformer.
It was unreliable.

Therefore, an object of the present invention is to provide a piezoelectric transformer which solves the above problems and has a high reliability and a high step-up ratio.

[0016]

According to the present invention, in a piezoelectric transformer utilizing a longitudinal resonance mode of a piezoelectric ceramic rectangular plate, about 1/6 from one end in the longitudinal direction is a center. / 3, the surface electrodes facing each other in the thickness direction are formed, and the other end is 1/2, 1/3, 1 /
Strip-shaped electrodes, which are orthogonal to the length direction and are opposed to each other in the thickness direction, are formed at positions 6, and the portion sandwiched by the surface electrodes of the piezoelectric ceramic rectangular plate is polarized in the thickness direction and sandwiched by the strip electrodes. A piezoelectric transformer characterized by using piezoelectric ceramic rectangular plates that are polarized in the lengthwise direction in the directions facing each other.

According to the present invention, in the above piezoelectric transformer, a piezoelectric transformer is obtained in which the surface electrode serves as an input side terminal and at least one of the strip electrodes serves as an output side terminal.

According to the present invention, in the piezoelectric transformer utilizing the resonance mode in the length direction of the piezoelectric ceramic rectangular plate, a plurality of ceramic green sheets having internal electrodes printed with a metal paste are laminated and integrally sintered. A piezoelectric ceramic rectangular plate obtained by the above, having a size of about ⅓ centered on a position ⅙ from one end in the length direction,
A plurality of opposed internal electrodes that are alternately exposed on the two side surfaces are formed, and a plurality of strip-shaped internal electrodes that are orthogonal to the length direction are formed at positions of 1/2, 1/3, and 1/6 from the other end. A piezoelectric transformer characterized by using a piezoelectric ceramic rectangular plate formed and further having external electrodes connected to the side surfaces of the facing and strip-shaped internal electrodes is obtained.

According to the present invention, in the piezoelectric transformer, the opposed internal electrode portions are polarized in the thickness direction of the rectangular plate, and the strip-shaped internal electrode portions are polarized in the direction facing each other and in the length direction. A piezoelectric transformer characterized by the above is obtained.

According to the present invention, in the piezoelectric transformer, the external electrode provided on the counter internal electrode serves as an input side terminal, and at least one of the external electrodes provided on the strip-shaped internal electrode serves as an output side terminal. A characteristic piezoelectric transformer is obtained.

Since the bulk type piezoelectric transformer of the present invention does not have a common terminal for the input side terminal and the output side terminal, a full bridge circuit can be used, and a double boosting ratio can be obtained.
Moreover, the strip electrodes 13a, 13b-14a, 1 of FIG.
The positive and negative strains between 4b and between 14a, 14b-15a, 15b are opposite [FIG. 2 (c)], but the strip electrodes 13a, 13b.
To 14a, 14b and 15a, 15b to 14a, 1
4b, or 14a, 14b to 13a, 13b
Since the polarized plates are polarized in the length direction of the rectangular plate in the directions from 14a, 14b to 15a, 15b, the polarities of the generated voltages are the same, and the output voltage is not lost. Further, since the terminals can be taken out from the node point on both the input side and the output side, it is possible to provide a highly reliable piezoelectric transformer.

Further, since the laminated piezoelectric transformer of the present invention has no common terminal for the input side terminal and the output side terminal and is electrically insulated, a full bridge circuit can be used and a double boosting ratio can be obtained. can get. In addition, the positive and negative strains between the internal electrodes 12-13 and 13-14 in FIGS. 1B and 1C are opposite [FIG. 2C], but the internal electrodes 12 to 13 and 14 To 13 or 13 to 12 and 13 to 14 are polarized in the length direction of the rectangular plate, the polarities of the generated voltages are the same and the output voltage is not lost.
Moreover, since the input-side internal electrodes are laminated, the capacitance is large, and the ratio of the capacitances on the input side and the output side is large, and as a result, a high boosting ratio can be obtained. Furthermore, the terminals can be taken out from the node point on both the input side and the output side, and since the input terminal and the output terminal are electrically insulated, a highly reliable piezoelectric transformer is provided. can do.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

(Embodiment 1) FIG. 1A shows the first embodiment of the present invention.
FIG. 3 is an explanatory view of the piezoelectric transformer of the embodiment. 42m long
The surface electrodes 12a and 12b having a length of 14 mm are formed on a PZT-based piezoelectric ceramic rectangular plate 11 having a size of m, a width of 10 mm, and a thickness of 1 mm by using a silver paste, centering at a position 7 mm from one end in the length direction. , 21 from the other end
1 mm wide strip electrode 1 at the positions of mm, 14 mm and 7 mm
3a, 13b, 14a, 14b, 15a, 15b were formed.

This ceramic rectangular plate 11 is used as a surface electrode 12
a-12b is polarized in the thickness direction (arrow 16a), and strip electrodes 13a, 13b to 14a, 14b and 15a, 1
5b to 14a and 14b were polarized in the longitudinal direction (arrows 16b and 16c).

Polarization is carried out at a temperature of 150 ° C. and an electric field strength of 1.2 k.
V / mm.

The terminals are taken out from the centers of the strip electrodes 12a and 12b, that is, the node points, and the input side terminals 17a and 17b.
Similarly, the electrodes 13b and 15a at the node point
Then, the terminals were taken out, and the output side terminals 18a and 18b were piezoelectric transformers in the length-wise 3/2 wavelength resonance mode.

The piezoelectric transformer of the present embodiment and the conventional longitudinal direction 3/2 shown in FIG. 3 (Comparative example 1) and FIG. 4 (Comparative example 2).
Table 1 shows a comparison with a wavelength resonance mode piezoelectric transformer.

[0029]

As is clear from Table 1, in the piezoelectric transformer of the present invention, since the full bridge circuit can be used, the step-up ratio that is twice that of the piezoelectric transformer of Comparative Example 1 is obtained. Even when compared with the piezoelectric transformer of Comparative Example 2 in which the full bridge circuit can be used, the boosting ratio is lower than that of the piezoelectric transformer of the present invention because the capacitance on the input side is small. Further, when the piezoelectric transformer was continuously driven, in the piezoelectric transformer of Comparative Example 2, there was a terminal that could not be taken out from the node point, so that the terminal was disconnected. There was no problem because it was taken out.

(Embodiment 2) In FIGS. 1 (b) and 1 (c),
1 shows a piezoelectric transformer according to a second embodiment of the present invention.
1B is a side view thereof, and FIG. 1C is a plan view thereof.

First, a method of manufacturing the piezoelectric transformer according to this embodiment will be described. On the PZT-based piezoelectric ceramic green sheets with a thickness of 210 μm and 60 μm, silver-
Print the internal electrode pattern with palladium electrode paste.

An internal electrode 11a having a length of 14 mm is formed around a position 7 mm from one end in the length direction, and internal electrodes 12, 13 and 14 having a width of 1 mm are formed at positions 21 mm, 14 mm and 7 mm from the other end. did.

Five layers of 210 μm printing sheets were laminated on a 60 μm printing sheet, and 60 without an electrode pattern was formed thereon.
One μm sheet is laminated, and the laminated body is thermocompression bonded and sintered in the air to obtain a piezoelectric ceramic rectangular plate 1 having a length of 42 mm, a width of 10 mm and a thickness of 1 mm.

Further, using silver paste, external electrodes 15A, 15B, 16A, 16B, 17A, 17 connected to internal electrodes are formed on the long side surfaces of the obtained piezoelectric ceramic rectangular plate 1.
B, 18A and 18B are formed.

This piezoelectric ceramic rectangular plate is used as an external electrode 1.
Polarized in the thickness direction of the rectangular plate between 5A and 15B, and the external electrodes 16A and 16B to 17A and 17B and 18A and 18B.
To 17A and 17B, the light was polarized in the length direction of the rectangular plate.

Polarization is carried out at a temperature of 150 ° C. and an electric field strength of 1.2 k.
V / mm.

The terminals are taken out from the centers of the external electrodes 15A and 15B, that is, the node points to be the input side terminals 2a and 2b. Similarly, the terminals are taken out from the external electrode 16A and the external electrode 18BA at the node points, and the output side terminals 3a and 2a. As 3b, a piezoelectric transformer of 3/2 wavelength resonance mode in the longitudinal direction is used.

The piezoelectric transformer of the present embodiment and the conventional length direction 3/2 shown in FIG. 3 (Comparative Example 1) and FIG. 4 (Comparative Example 2).
Table 2 shows a comparison with the piezoelectric transformer of the wavelength resonance mode.

[0040]

As is clear from Table 2, in the piezoelectric transformer of the present invention, a full bridge circuit can be used, and the input side has a large capacitance due to the laminated structure. Therefore, compared with the piezoelectric transformer of Comparative Example 1. 7 times, and a boosting ratio of 4.5 times as compared with Comparative Example 2 are obtained. Further, when the piezoelectric transformer was continuously driven, in the piezoelectric transformer of Comparative Example 2, there was a terminal that could not be taken out from the node point, so that the terminal was disconnected. There was no problem because it was taken out.

[0042]

As described above, according to the present invention, a highly reliable piezoelectric transformer having a high step-up ratio can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a piezoelectric transformer of the present invention. FIG.
(A) is a perspective view of the piezoelectric transformer of the 1st example of the present invention. FIG. 1B is a side view of the piezoelectric transformer according to the second embodiment of the present invention. FIG. 1C is a plan view of a piezoelectric transformer according to a second embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation principle of a piezoelectric transformer vibrating in a resonance mode. FIG. 2A is a side view of the piezoelectric ceramic rectangular plate. FIG. 2B is a diagram showing a displacement distribution when the piezoelectric ceramic rectangular plate vibrates in the 3/2 wavelength resonance mode of longitudinal vibration. FIG. 2C is a diagram showing a strain distribution when the piezoelectric ceramic rectangular plate vibrates in the 3/2 wavelength resonance mode of longitudinal vibration.

FIG. 3 is a perspective view of a conventional piezoelectric transformer.

FIG. 4 is a perspective view of another conventional piezoelectric transformer.

[Explanation of symbols]

1, 11, 31, 41 Piezoelectric ceramic rectangular plates 2a, 2b, 17a, 17b, 36a, 36b, 47
a, 47b Input side terminals 3a, 3b, 18a, 18b, 37a, 37b, 48
a, 48b Output side terminals 11a, 12, 13, 14 Internal electrodes 12a, 12b, 32a, 32b, 42a, 42b, 4
3 surface electrodes 13a, 13b, 14a, 14b, 15a, 15b, 3
3a band-shaped electrodes 33b, 34a, 34b, 44a, 44b, 45a, 4
5b Strip-shaped electrodes 15A, 15B, 16A, 16B External electrodes 17A, 17B, 18A, 18B External electrodes 16a, 16b, 16c, 35a, 35b, 35c
Arrows 46a, 46b, 46c (indicating polarization direction) Arrows 21a, 21b, 21c (indicating polarization direction) Node points

Claims (5)

[Claims] 1. A piezoelectric transformer utilizing a resonance mode in a length direction of a piezoelectric ceramic rectangular plate, having a length of about 1/3 from a position of 1/6 from one end in the length direction,
The surface electrodes facing each other in the thickness direction are formed, and the strip electrodes, which are orthogonal to the length direction and are opposed to each other in the thickness direction, are formed at positions of 1/2, 1/3 and 1/6 from the other end. A piezoelectric transformer comprising: a piezoelectric ceramic rectangular plate in which the surface electrode portions are polarized in the thickness direction and the strip electrode portions are polarized in the direction facing each other and in the length direction. 2. The piezoelectric transformer according to claim 1, wherein
A piezoelectric transformer characterized in that a surface electrode serves as an input side terminal and at least one of the strip electrodes serves as an output side terminal. 3. A piezoelectric transformer which utilizes a resonance mode in the lengthwise direction of a piezoelectric ceramic rectangular plate, wherein a plurality of ceramic green sheets having internal electrodes printed with a metal paste are laminated and integrally sintered to obtain a piezoelectric element. A ceramic rectangular plate having a plurality of opposing internal electrodes alternately exposed on two side faces, each having a size of about 1/3, centered at a position 1/6 from one end in the longitudinal direction, A plurality of strip-shaped internal electrodes that are orthogonal to the lengthwise direction are formed at positions of 1/2, 1/3, and 1/6 from the other end, and the external electrodes are connected to the side surfaces of the facing and strip-shaped internal electrodes, respectively. A piezoelectric transformer comprising a piezoelectric ceramic rectangular plate having electrodes formed thereon. 4. The piezoelectric transformer according to claim 3, wherein
The opposing internal electrode portions are polarized in the thickness direction of the rectangular plate,
A piezoelectric transformer characterized in that strip-shaped internal electrode portions are polarized in a direction facing each other and in a length direction. 5. The piezoelectric transformer according to claim 3, wherein the external electrode provided on the opposing internal electrode is an input side terminal, and at least one of the external electrodes provided on the strip internal electrode is an output side terminal. Piezoelectric transformer characterized by that.