JPH1070319A - Multilayer piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent lowering of efficiency and short circuit by providing an electrode layer for input with a leading out part which faces the side face of a piezoelectric layer and sufficiently narrowing the width of the leading out part compared with that of the electrode layer. SOLUTION: An inner electrode for input is formed in a piezoelectric body, except the leading out part, and is lead out to the side face of the piezoelectric body at the leading out part. The inner electrode is formed in the same shape so as to be superposed when viewed in the stacking direction. A pair of input electrodes 55 are formed on the upper and lower faces, and on the side face, a connecting electrode 56, which connects the leading out part which is lead out to the side face, is formed for continuity to respective upper and lower input electrodes 55. On the both edge planes of the multilayer piezoelectric transformer 59, output electrodes 57 are formed. Lead lines 58 are soldered to the upper and lower input electrodes 55 at the center. Thus, stress concentration while being driven is prevented and short circuit is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric transformer used for voltage conversion.

[0002]

2. Description of the Related Art In recent years, power supply circuits such as a backlight inverter and a DC / DC converter for a liquid crystal display using a piezoelectric transformer have been actively studied.
The reason for this is that the adoption of the piezoelectric transformer makes it possible to realize a drastic reduction in size and thickness of the power supply circuit.

FIG. 10 shows an example of a piezoelectric transformer for this power supply circuit. This piezoelectric transformer is a Rosen type piezoelectric transformer, for example, a lead zirconate titanate (PZT).
A pair of input electrodes 4, 6 provided by, for example, silver baking is formed on the upper and lower surfaces of the left half of the plate-shaped piezoelectric ceramic element 2 in the figure, and an output electrode 8 is formed on the right end face in the same manner. I have. The left half driving portion of the piezoelectric ceramic element 2 is polarized in the thickness direction, and the right half power generating portion is polarized in the length direction as indicated by arrows.

In the piezoelectric transformer thus formed, when an AC voltage having substantially the same frequency as the longitudinal resonance frequency of the piezoelectric ceramic element 2 is applied between the input electrodes 4 and 6 from the AC voltage source 10, the piezoelectric ceramic The element 2 generates a strong mechanical vibration in the longitudinal direction, whereby electric charges are generated by the piezoelectric effect in the right half of the power generation unit, and an output voltage Vo is generated between the output electrode 8 and one of the input electrodes, for example, the input electrode 6. Occurs. FIG. 1 shows the vibration mode of the piezoelectric ceramic element 2.
As shown in FIG. 1A, a half-wavelength mode (λ / 2 mode) that resonates at a half wavelength in the length direction, and a one-wavelength mode (λ mode) that resonates at one wavelength as shown in FIG. 11B. There is.

When driven at the same frequency, the element of the piezoelectric transformer driven in the one-wavelength mode is twice as long as the element driven in the half-wave mode. For this reason, the piezoelectric transformer driven in the half-wave mode can be made smaller than the piezoelectric transformer driven in the one-wave mode. On the other hand, in terms of the boost ratio, the one-wavelength mode can obtain a higher boost ratio than the half-wave mode.

In addition to the single-plate type piezoelectric transformer shown in FIG. 10, a laminated type piezoelectric transformer has been proposed. FIG. 12 shows an example of this laminated type. In the laminated piezoelectric transformer element 1, input electrodes 3 and 5 are formed in the front half in the figure, and an output electrode 7 is formed on the other end surface. This input electrode is also formed in the element 1 alternately with the piezoelectric ceramic material.
The input electrodes 3, 3a, 3b, 5, 5a, 5b are connected alternately. That is, the input electrodes 3, 3a, 3
b are connected by the connection electrodes 9 on the side surfaces, and the input electrodes 5, 5a,
5b is connected by the connection electrode 11 on the other side. Then, this laminated piezoelectric transformer can constitute a piezoelectric transformer having a higher step-up ratio than a single-plate type structure.

As described above, in consideration of miniaturization, a stacked type piezoelectric transformer is more advantageous than a single plate type in order to drive in a half wavelength mode rather than a single wavelength mode and to obtain a high boosting ratio. It can be seen that it is.

[0008]

From the above, the present inventors have previously proposed a structure in which an input electrode is arranged at the center of a laminated piezoelectric transformer. In the present invention, various studies have been made on the structure of the input internal electrode of the central driving type laminated piezoelectric transformer.

First, FIG. 5 is a plan view showing the internal electrode structure of the comparative example. In this comparative example, the input internal electrodes 22 are alternately shifted to the center of the piezoelectric layer 21 so that one internal electrode faces one side surface. FIG. 6 shows the connection state of the internal electrodes after lamination in this comparative example.
In this comparative example, as shown in FIG.
3 occurs on the side. This portion is horizontally polarized in the width direction of the element at the time of polarization. As a result, at the time of driving, vibration of a mode different from the vibration of the portion where the internal electrodes are opposed to each other is generated. Cause problems.

Next, FIG. 8 is a plan view showing the internal electrode structure of another comparative example. In this comparative example, the input internal electrodes 27 are formed at the center of the piezoelectric layer 26, but the cutouts 28 are provided alternately. By forming the notches 28 alternately, as shown in FIG.
Is formed, and desired internal electrodes can be connected to each other. In the case of this comparative example, stress concentration during driving can be considerably reduced. However, since the input internal electrodes are exposed close to each other on the side surface, there is a danger of short-circuiting when driving under high humidity, such as minute dew condensation on the element surface (side surface) immediately causing a short circuit on the input side. Is not preferred.

In view of the above, the present invention examines the structure of the input internal electrode in a center laminated type laminated piezoelectric transformer, and provides a laminated type piezoelectric transformer which does not cause a reduction in efficiency and a short circuit. Things.

[0012]

According to the present invention, a rectangular piezoelectric layer and input internal electrode layers formed in the center of the piezoelectric layer are alternately laminated, and output electrodes are provided on both end faces. In the formed laminated piezoelectric transformer, the input internal electrode layer has a lead portion facing a side surface of the piezoelectric layer, and the width of the lead portion is sufficiently smaller than the width of the electrode layer. is there.

The present invention also relates to a laminated type in which rectangular piezoelectric layers and input internal electrode layers formed in the center of the piezoelectric layers are alternately laminated, and output electrodes are formed on both end faces. In the piezoelectric transformer, the input internal electrode layer has a lead portion facing the side surface of the piezoelectric layer, the width of the lead portion is sufficiently smaller than the width of the electrode layer, and the lead portion is The lead-out portions of the input internal electrodes which are formed closer to any one of the end faces than the central axis of the input internal electrodes, and are drawn out to the other side surfaces and the other end face sides, respectively. Further, according to the present invention, a connection electrode for connecting the lead-out portion is formed on a side surface of the laminate, and the connection electrodes are respectively connected to input electrodes on the upper and lower surfaces of the laminate, and a lead is provided on the input electrode. The wires are connected, and the lead wires on the upper and lower surfaces are connected to be shifted to different end surfaces.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, an input internal electrode is formed in the center of a rectangular piezoelectric layer inside without facing a side face, and is configured to face each other in the same region.
The lead portion is formed to be sufficiently narrower than the internal electrode. The width of the lead portion may be any width as long as connection between the layers is possible.

According to the present invention, the opposing electrodes have the same shape,
Since they are overlapped, polarization in the horizontal direction can be prevented except in a narrow region of the drawer. Moreover, since the internal electrode is formed inside except for the lead-out portion, it is possible to prevent a short circuit on the side surface. Also, since only the electrodes to be connected on the side face the side surface, the connection can be made easily and there is no danger of short circuit.

Further, in the present invention, the lead portions of the internal electrodes facing each other are shifted to the opposite end faces, and the lead wires for external connection are similarly shifted to each other. The short circuit in the lead wire is prevented.

[0017]

FIG. 1 is a perspective view showing one embodiment of the present invention. FIG. 2 is a plan view showing the state of the internal electrodes of this embodiment. In this embodiment, as shown in FIG. 2, an input internal electrode 52 is printed on a green sheet 51 of a piezoelectric ceramic by printing a pattern of a conductor (Ag / Pd paste or the like).
A predetermined number of the green sheets are laminated, pressed and fired to obtain a laminated piezoelectric transformer. The input internal electrode 52 of this embodiment is formed inside the piezoelectric body except for the lead-out portion 53, and is drawn out to the side surface of the piezoelectric body by the lead-out portion 53. The input internal electrodes 52 have the same shape and are formed so as to overlap each other when viewed in the laminating direction, except for the lead-out portions 53.

In this embodiment, as shown in FIG. 1, a pair of input electrodes 55 are formed on upper and lower surfaces, and connection electrodes 56 are formed on the side surfaces to connect the lead portions drawn out to the side surfaces. It is electrically connected to the upper and lower input electrodes 55. Output electrodes 57 are formed on both end surfaces of the laminated piezoelectric transformer 59. Lead wires 58 are soldered to the upper and lower input electrodes 55. At this time, the lead wire 58 is soldered at the center of the input electrode 55.

FIG. 3 is a perspective view of another embodiment according to the present invention. FIG. 4 is a plan view showing the state of the internal electrodes of this embodiment. In this embodiment, as shown in FIG. 4, an input internal electrode 62 and a lead portion 63 are formed on a green sheet 61 of a piezoelectric ceramic by pattern printing of a conductor, and a predetermined number of the green sheets are laminated. , Pressed and fired to obtain a laminated piezoelectric transformer. The input internal electrode 62 of this embodiment is formed inside the piezoelectric body except for the lead-out portion 63, and is drawn out to the side surface of the piezoelectric body by the lead-out portion 63. Then, the input internal electrode 62
Are formed in the same shape as seen in the laminating direction, and are formed so as to overlap each other, except for the drawer 63.

In this embodiment, the lead-out portion 63 is formed so as to be shifted to one of the end surfaces with respect to the center axis 64 of the input internal electrode 62, and furthermore, the input internal electrode 62 which faces the input electrode 62.
In between, the drawers 63 are located on opposite sides and opposite end faces.

In this embodiment, as shown in FIG. 3, a pair of input electrodes 65 are formed on the upper and lower surfaces, and connection electrodes 66 for connecting the lead portions drawn out to the side surfaces are formed on the side surfaces. It is electrically connected to the upper and lower input electrodes. Output electrodes 67 are provided on both end faces of the laminated piezoelectric transformer 69.
Are formed. Lead wires 68 are soldered to the upper and lower input electrodes 65. In this embodiment, since the lead portions 68 are shifted and connected in addition to the shifted lead portions 63, it can be seen that the effect of preventing a short circuit between the input electrodes is high.

In the above two embodiments, the central drive type piezoelectric transformer has an input electrode arranged at the center of the element, and is constituted by a laminated type. This driving method is 1
A / 2λ type piezoelectric transformer was constructed. As a result, a piezoelectric transformer having a small size and a high step-up ratio could be configured.

[0023]

According to the present invention, a laminated piezoelectric transformer having a structure in which stress concentration at the time of driving is prevented and a short circuit is prevented can be formed. In addition, a piezoelectric transformer having a central drive type, a small size and a high step-up ratio can be obtained. be able to.

[Brief description of the drawings]

FIG. 1 is a perspective view of an embodiment according to the present invention.

FIG. 2 is a plan view showing a state of an input internal electrode of the embodiment of FIG.

FIG. 3 is a perspective view of another embodiment according to the present invention.

FIG. 4 is a plan view showing a state of an input internal electrode of the embodiment of FIG. 3;

FIG. 5 is a plan view showing a state of an input internal electrode of a comparative example according to the present invention.

FIG. 6 is a perspective view of the comparative example of FIG.

FIG. 7 is a cross-sectional view of the comparative example of FIG.

FIG. 8 is a plan view showing a state of an input internal electrode of another comparative example according to the present invention.

FIG. 9 is a perspective view of the comparative example of FIG.

FIG. 10 is a perspective view of a conventional example.

FIG. 11 is a diagram showing a state of vibration in the case of a half-wavelength mode and a one-wavelength mode.

FIG. 12 is a perspective view of a conventional example.

[Explanation of symbols]

 51, 61 Green sheet of piezoelectric ceramic (piezoelectric layer) 52, 62 Input internal electrode 53, 63 Leader 55, 65 Input electrode 56, 66 Connecting electrode 57, 67 Output electrode 58, 68 Lead wire 59, 69 Stack Type piezoelectric transformer 64 center axis

[Procedure amendment]

[Submission date] March 5, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG.

Claims (3)

[Claims] 1. A rectangular piezoelectric layer and input internal electrode layers formed at the center of the piezoelectric layer are alternately laminated,
In the laminated piezoelectric transformer having output electrodes formed on both end surfaces, the input internal electrode layer has a lead portion facing a side surface of the piezoelectric layer, and the width of the lead portion is larger than the width of the electrode layer. The multilayer piezoelectric transformer is also characterized by being sufficiently narrow. 2. A rectangular piezoelectric layer and an input internal electrode layer formed at the center of the piezoelectric layer are alternately laminated,
In the laminated piezoelectric transformer having output electrodes formed on both end surfaces, the input internal electrode layer has a lead portion facing a side surface of the piezoelectric layer, and the width of the lead portion is larger than the width of the electrode layer. Is sufficiently narrow, and the lead-out portion is formed closer to one of the end faces than the center axis of the input internal electrode, and the lead-out portions of the opposing input internal electrode are formed on different side surfaces and separately. Characterized in that it is drawn out to the end face side. 3. The laminate according to claim 2, wherein:
A connection electrode for connecting the lead-out portion is formed, and the connection electrode is connected to input electrodes on the upper and lower surfaces of the laminate, respectively, and a lead wire is connected to the input electrode. , Each of which is connected to a different end face side.