JP2003086857A - Piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated piezoelectric transformer that can highly safely prevent the breakage of a piezoelectric vibrator even when the transformer is used to supply electric power to a converter by preventing the occurrence of electric field concentration in the vibrator. SOLUTION: The square plate-shaped piezoelectric vibrator 20 composed of a piezoelectric ceramic material of the piezoelectric transformer is divided into two equal parts of an input section 22 and an output section 23 as compared with the conventional piezoelectric vibrator. The whole structure of the vibrator 20 in which an insulating layer 24 is arranged in a central area defining the boundary between the input and output sections 22 and 23 and the internal structure of the vibrator 20 indicating the pattern of internal electrodes for input and output (including circular internal electrodes) in the input and output sections 22 and 23 are similar to those of the conventional piezoelectric vibrator. However, it is different from the conventional vibrator that a pair of external electrodes 27a and 27b for input and a pair of external electrodes 28a and 28b for output exposed on the side faces of the vibrator 20 for connecting the internal electrodes for input and output are arranged so that they respectively stay in the areas of the input section 22 and output section 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is mainly suitable as a converter power supply and also has a laminated structure piezoelectric transformer which utilizes radial vibration (resonance mode) on either the input side or the output side or both of them. Regarding

[0002]

2. Description of the Related Art Recently, the demand for piezoelectric transformers as a power source for liquid crystal backlights of notebook type personal computers has been rapidly increasing. This is a direct current (D
C) Thickness of several mm from voltage to high voltage of several hundreds V
This is because various problems occur in the well-known electromagnetic inverter in order to obtain it under the installation condition in which the thinning tendency is regulated to some extent. In addition, an inverter that can boost the voltage to ultra high voltage has been developed, but such an inverter is in a very special category as a power source.

Therefore, a piezoelectric transformer utilizing a resonance mode in the radial direction of a rectangular plate-shaped piezoelectric vibrator having a laminated structure made of a piezoelectric ceramic material is expected to be applied to applications having a relatively small load impedance. In such a laminated structure, a square plate-shaped piezoelectric vibrator that is easy to manufacture is used to perform step-up / down by utilizing contour vibration in the radial direction, and a circular internal electrode is most suitable.

FIG. 6 shows the basic structure of a conventional piezoelectric transformer. FIG. 6 (a) shows an exploded perspective view showing a laminated pattern of internal electrodes, and FIG. 6 (b) shows the whole. External perspective view, Figure (c) is the same as Figure (b)
2 is a side cross-sectional view taken along the line AA ′ of FIG.

This piezoelectric transformer is shown in FIGS. 6 (a) to 6 (c).
Referring to, the vertical and horizontal dimensions are 20 mm on a side and the thickness is 6.
It is composed of a square plate-shaped piezoelectric vibrator 10 made of a 0 mm laminated piezoelectric ceramic material. This square plate-shaped piezoelectric vibrator 10 is divided into two equal parts in the thickness direction, one of which has a thickness of 2.
4 mm input part 12 and the other 2.1 mm thick output part 1
3, and an insulating layer 14 made of a piezoelectric ceramic material having a thickness of 1.5 mm is arranged in the central region which is the boundary between the input section 12 and the output section 13.

Of these, the input portion 12 has a square thickness 1. of a piezoelectric ceramic material having one polarity as an electrode pattern inside the square plate-shaped piezoelectric vibrator 10.
A circular plate having a thickness of 1.2 mm, which is a circular internal electrode 2c formed on a 2 mm thin plate-shaped ceramic sheet and extends locally to one side peripheral edge of the input internal electrode 15a and a piezoelectric ceramic material having the other polarity. The circular internal electrodes 2d formed on the cylindrical ceramic sheet and local portions extending to one side peripheral edge of the input internal electrode 15b are alternately exposed and disposed on the side surfaces facing each other in one direction of the square plate piezoelectric vibrator 10. Each of the thin plate-shaped ceramic sheets is laminated as described above, and the input internal electrodes 15a and 15b each have a two-layer structure polarized in the laminating direction (thickness direction). Input internal electrodes 15a, 15 exposed on the side surfaces of the child 10 facing each other in one direction
External input electrodes 17a and 17b for supplying input signals are respectively provided in b so as to extend and be connected to the whole in the stacking direction.

On the other hand, the output section 13 is a square thin ceramic sheet having a thickness of 0.35 mm made of a piezoelectric ceramic material having one polarity as an electrode pattern in the inside of the square piezoelectric vibrator 10. Output internal electrode 16a by the formed circular internal electrode 2a
A circular internal electrode 2 formed on a thin plate-shaped ceramic sheet having a thickness of 0.35 mm, which is a square and is made of a piezoelectric ceramic material having the other side and a local side extending to one side edge.
Local portions of the output internal electrode 16b extending to the peripheral edge on one side are alternately exposed to the side surfaces facing each other in one direction perpendicular to another direction on the same plane as one direction of the square plate piezoelectric vibrator 10. Stack each thin plate-like ceramic sheet,
Further, these output internal electrodes 16a and 16b have a six-layer structure in which they are polarized in opposite directions to each other in the stacking direction, and are further exposed to the side surfaces facing each other in the other direction. The output internal electrodes 16a and 16b are respectively provided with output external electrodes 18a and 18b for extracting output signals so as to extend and be connected to the entire output direction in the stacking direction.

That is, in the input section 12 and the output section 13, the input internal electrodes 15a and 15b and the output internal electrode 1 are provided.
Since the local portions of 6a and 16b are regularly exposed on the side surface of the square plate-shaped piezoelectric vibrator 10, the input external electrodes 17a and 17b are formed.
b and the output internal electrodes 18a and 18b, the input internal electrodes 15a and 15b and the output internal electrode 16a,
16b has a simple structure for taking out terminals.

The piezoelectric transformer having such a laminated structure is
When an AC voltage close to the resonance frequency (about 100 kHz) is applied to the two input external electrodes 17a and 17b,
Since the transformed voltage can be taken out between the two output external electrodes 18a and 18b, it has been put to practical use as a step-up transformer for a liquid crystal backlight, and also as a step-down piezoelectric transformer for a converter power supply with a larger market. The use of is also being considered. Incidentally, the overall shape is shown in FIG.
Other than the square plate shape shown in (a) to (c), it is possible to make a rectangular plate shape.

[0010]

The above-mentioned conventional laminated type piezoelectric transformer is characterized in that the input portion and the output portion are structurally divided in the laminating direction with the insulating layer interposed therebetween. Considering the applicability as a step-down piezoelectric transformer for a converter power supply, a dielectric strength of several kv is required between the input side terminal and the output side terminal of the power supply transformer as a safety standard for AC-DC converters and the like. As opposed to
Withstand voltage of piezoelectric ceramic material is 10k per 1mm
Although it is considered that it is possible to sufficiently cope with the fact that there is about v, in reality, for example, a strong electric field concentration occurs in the area E shown in FIG. There is a problem of destruction.

FIG. 7 shows that the DC voltage of 5 kV is applied between the input and output terminals connected to the external input electrodes and the external output electrodes for the converter power supply using the piezoelectric transformers shown in FIGS. Element analysis (FE
(A) is a schematic view of the electric field intensity distribution obtained as a result of the electric field analysis by (M). FIG. (A) relates to a perspective view including the direction of the electric field in the overall appearance, and (b) of the same figure. FIG. 1A relates to a side sectional view including the direction of the electric field in the direction of the cutting plane M, and FIG. 1C relates to an enlarged view including the direction of the electric field obtained by enlarging a local portion of FIG. Note that X and Y in FIG. 7A are axial directions that determine the plane direction, and Z in FIG. 7B is an axial direction that determines the height direction with respect to the XY plane.

From FIGS. 7 (a) to 7 (c), as a result of the electric field analysis, a uniform electric field is obtained in the regions E3 and E4 in the vicinity of the central portion of the square plate piezoelectric vibrator near the insulating layer. On the other hand, the electric field is remarkably concentrated in the areas E1 and E2 in the vicinity of the side surface where the input external electrode and the output external electrode on the peripheral side are arranged (in the figure, the size of the arrow indicates each analysis point). The electric field strength is shown in Fig. 4, and the state in which a plurality of arrows extend from one point in different directions indicates the concentration of the electric field. Especially, the insulating layer in the region E2 is closest to each external electrode on the side surface. It can be seen that there is a tendency for the concentration of the electric field to become noticeable in the part where Therefore, the concentration of the electric field in the peripheral portion typified by the regions E1 and E2 causes structural damage because it causes destruction of the piezoelectric vibrator. In the case of a piezoelectric vibrator, a structure in which an input external electrode and an output external electrode for connecting the exposed portions of the input internal electrode and the output internal electrode on the side surface are arranged so as to extend in the entire stacking direction. Has been found to have room for improvement.

The present invention has been made to solve such problems, and its technical problem is that even if it is used for a converter power supply, local concentration of an electric field hardly occurs in a piezoelectric vibrator. It is another object of the present invention to provide a piezoelectric transformer having a laminated structure that can prevent damage with high safety.

[0014]

According to the present invention, a rectangular thin plate-shaped ceramic sheet including a square made of a piezoelectric ceramic material, in which a circular internal electrode including a local portion extending to one side edge is arranged, is formed into a circular shape. The input part and the output part are divided in the stacking direction by alternately stacking so that the local parts of the internal electrodes face each other in one direction and another direction perpendicular to the one direction, and the input part And a rectangular plate-shaped piezoelectric vibrator having a laminated structure in which an insulating layer made of the piezoelectric ceramic material is interposed between the output parts in the stacking direction, and the rectangular plate-shaped piezoelectric vibrator is provided on a side surface of the rectangular plate-shaped piezoelectric vibrator. A pair of input external electrodes are arranged so as to be connected to each other in the laminating direction on the local part of the circular internal electrode that is exposed to face, and is provided on the side surface of the rectangular plate-shaped piezoelectric vibrator in the other direction. Of the circular internal electrodes exposed facing each other A pair of output external electrode in disposed the piezoelectric transformer so as to connect with the lamination direction section,
A pair of input external electrodes are provided so as to be included in the area of the input section, and a pair of output external electrodes are provided so as to be included in the area of the output section.

Further, according to the present invention, a rectangular thin plate-shaped ceramic sheet including a square made of a piezoelectric ceramic material, in which a circular internal electrode including a local portion extending to a peripheral edge of one corner is disposed, is a local portion of the circular internal electrode. Are alternately laminated so that they are opposed to each other in a diagonal direction and other diagonal directions perpendicular to each other on the same plane, and the input part and the output part are divided in the stacking direction, and the input A rectangular plate-shaped piezoelectric vibrator having a laminated structure in which an insulating layer made of the piezoelectric ceramic material is interposed in the stacking direction between the output part and the output part, and the pair of piezoelectric plates is provided on a side surface of the rectangular plate-shaped piezoelectric vibrator. A pair of input external electrodes are provided so as to extend and connect to the local portions of the circular internal electrodes that are exposed facing each other in the angular direction, and are provided on the side surfaces of the rectangular plate-shaped piezoelectric vibrator. Exposed opposite the other diagonal direction A piezoelectric transformer is obtained a pair of output external electrodes to the local areas of circular shape internal electrode is disposed so as to be connected extending over the entire of the laminated direction of.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the piezoelectric transformer of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a basic structure of a piezoelectric transformer according to an embodiment of the present invention. FIG. 1 (a) relates to an external perspective view showing the whole, and FIG. 1 (b) shows the whole. The side view from the one direction shown in the figure, and the figure (c) relate to the side sectional view in the AA 'line direction of the figure (a) and its local enlarged view.

Also in the case of this piezoelectric transformer, FIG.
Similar to the conventional piezoelectric transformer shown in (c), it is composed of a square plate-shaped piezoelectric vibrator 20 made of a laminated piezoelectric ceramic material having a length and width of 20 mm on each side and a thickness of 6.0 mm. Referring to (a) to (c), the square plate-shaped piezoelectric vibrator 20 is divided into two parts in the thickness direction and one is thicker than the case of the square plate-shaped piezoelectric vibrator 10 of the conventional piezoelectric transformer. The input portion 22 having a thickness of 2.4 mm and the output portion 23 having a thickness of 2.1 mm on the other side have a thickness of 1.5 mm in the central region which is a boundary between the input portion 22 and the output portion 23. Insulating layer 24 made of piezoelectric ceramic material
Is common, and the internal structure showing the pattern of internal electrodes for input / output (including circular internal electrodes) in the input section 22 and the output section 23 is common, A pair of input external electrodes 27a, 27 for connecting the input / output internal electrodes exposed on the side surfaces.
The difference is that b and the pair of output external electrodes 28a and 28b are arranged so as to be housed in the regions of the input portion 22 and the output portion 23 in the stacking direction, respectively.

More specifically, in the case of this piezoelectric transformer, the input portion 22 has a square thickness of 1.2 mm and is made of a piezoelectric ceramic material having one polarity as an electrode pattern inside the square plate piezoelectric vibrator 20. A circular plate-shaped ceramic electrode 2c formed on a thin plate-shaped ceramic sheet and having a local portion extending to one side peripheral edge of the input internal electrode 25a and a piezoelectric ceramic material having the other polarity and having a square thickness of 1.2 mm. The circular internal electrodes 2d formed on the sheet and the local portions of the input internal electrodes 25b extending to the peripheral edge on one side are alternately exposed and arranged on the side surfaces facing each other in one direction of the square plate piezoelectric vibrator 20. Each thin plate-shaped ceramic sheet is laminated on the above, and these input internal electrodes 25a and 25b are polarized in the laminating direction (thickness direction), respectively. It has a two-layer structure, and further, the input internal electrodes 25a and 25b exposed on the side surfaces facing each other in one direction of the square plate-shaped piezoelectric vibrator 20 have input external electrodes for supplying input signals, respectively. 27a, 27b
Are arranged so as to be connected within the range of the input portion 22 in the stacking direction.

On the other hand, the output section 23 is also a square thin ceramic sheet having a thickness of 0.35 mm made of a piezoelectric ceramic material having one polarity as an electrode pattern in the inside of the square piezoelectric vibrator 20. Output internal electrode 26a by the formed circular internal electrode 2a
A circular internal electrode 2 formed on a thin plate-shaped ceramic sheet having a thickness of 0.35 mm and a square formed of a piezoelectric ceramic material having the other polarity and a local portion extending to one side edge.
Local portions of the output internal electrode 26b extending to the peripheral edge on one side are alternately exposed and exposed on side surfaces facing in one direction perpendicular to another direction on the same plane as one direction of the square plate piezoelectric vibrator 20. Stack each thin plate-like ceramic sheet,
In addition, these output internal electrodes 26a and 26b have a six-layer structure in which they are polarized in opposite directions to each other in the stacking direction, and are further exposed on the side surfaces facing each other in the other direction of the square plate piezoelectric vibrator 20. Output external electrodes 28a and 28b for extracting the output signal are arranged so as to be connected to the output internal electrodes 26a and 26b, respectively, within a range that is within the area of the output section 23 in the stacking direction.

That is, in this piezoelectric transformer, a circular thin plate-shaped ceramic sheet including a square made of a piezoelectric ceramic material, in which circular internal electrodes 2a to 2d including local portions extending to one side edge are arranged, is formed into a circular internal electrode 2a. The input parts 22 and the output part 23 are alternately laminated so that the local parts of 2d are opposed to each other in one direction and the other direction perpendicular to the same direction, and the input part 22 and the output part 23 are divided in the stacking direction. A rectangular plate piezoelectric vibrator 2 having a laminated structure in which an insulating layer 24 made of a piezoelectric ceramic material is interposed between the output portion 23 and the output portion 23 in the laminating direction.
0, which is a circular internal electrode 2c which is exposed on one side surface of the rectangular plate-shaped piezoelectric vibrator 20 so as to face each other in one direction.
A pair of input external electrodes 27a, 27b are arranged so as to be connected to the local portions of the input internal electrodes 25a, 25b by 2d so as to be connected in the stacking direction. Exposed circular internal electrodes 2a, 2b
When a pair of output external electrodes 28a, 28b are arranged so as to be connected to the local portions of the output internal electrodes 26a, 26b in the stacking direction, a pair of input external electrodes 27a,
27b is arranged so as to fit within the area of the input section 22, and the pair of output external electrodes 28a and 28b are arranged so as to fit within the area of the output section 23.

Also in the case of such a laminated type piezoelectric transformer, when an AC voltage close to the resonance frequency (about 100 kHz) is applied to the two input external electrodes 27a, 27b, the two output external electrodes 28a, The voltage transformed between 28b can be taken out.

Therefore, in the piezoelectric transformer of one embodiment, the two input external electrodes 27a and 27b are short-circuited and the two output external electrodes 28a and 28b are short-circuited to apply a DC voltage between the input and output terminals. As a result, the breakdown voltage was examined, and it was found that the breakdown voltage was 7.0 kV. Incidentally, in the case of the conventional piezoelectric transformer shown in FIGS. 6A to 6C, the breakdown voltage was 1.5 kV.

In general, the breakdown voltage of the piezoelectric ceramic material itself used for the piezoelectric transformer is about 10 KV / mm, so that some electric field concentration may cause a portion that partially reaches the breakdown voltage at a lower voltage. Therefore, I tried the electric field analysis by the finite element analysis also for the piezoelectric transformer here.

FIG. 2 shows a piezoelectric transformer according to one embodiment shown in FIGS. 1A to 1C, which is used as a converter power source, and is connected to an input external electrode and an output external electrode at 5 kV between input and output terminals. Shows the electric field strength distribution obtained as a result of the electric field analysis by the finite element analysis when the DC voltage is applied and is used. The figure (a) includes the direction of the electric field in the overall appearance. Perspective view, same figure (b)
Is a side sectional view including the direction of the electric field in the direction of the cutting plane M in FIG. 7A, and FIG. 7C is an enlarged view including the direction of the electric field obtained by enlarging a local portion of FIG. is there.

2A to 2C, as a result of the electrolytic analysis, the input external electrodes 27a and 27b and the output external electrode 28 on the peripheral side of the square plate piezoelectric vibrator 20 are obtained.
In the case of the conventional square plate piezoelectric vibrator 10 shown in FIGS. 7A to 7C, a plurality of arrows indicating the concentration of the electric field in the vicinity of the side surface where a and 28b are arranged are often generated. It does not exist at all in the seen region, and a substantially uniform electric field distribution can be obtained regardless of the region E5 near the insulating layer 24 or the region E6 in which the insulating layer 24 approaches each external electrode on the side surface. You can see that

Further, with respect to each of these piezoelectric transformers, the maximum electric field strength generated by the voltage application and the maximum stress generated by the voltage application were analyzed with a DC voltage of 5 kV being applied between the input and output terminals. In the transformer, the maximum electric field strength is 2 kV / mm and the maximum stress is 7 MPa.
However, in the conventional piezoelectric transformer, the maximum electric field strength is 6
The kV / mm and the maximum stress were 40 MPa.

As a result, in the case of the conventional piezoelectric transformer, the maximum electric field strength is 6 kV / mm in the region where the electric field is most concentrated.
The maximum stress value generated there reaches 40 MPa, which is of course not only a withstand voltage value as a piezoelectric element material, but considering that the tensile strength of a general piezoelectric ceramic material is about 30 MPa. If this is done, the size is large enough to cause destruction, but in the case of the piezoelectric transformer of one embodiment, the maximum electric field strength is 2 kV /
mm, the maximum stress value is only 7MPa, and since it does not cause dielectric breakdown until it reaches 7kV, the basic performance is greatly improved over conventional piezoelectric transformers, making it suitable as a step-down piezoelectric transformer for converter power supply. I understand.

By the way, in the piezoelectric transformer according to the embodiment, the external input electrodes 27a and 27b and the external output electrodes 28a and 2 arranged on the side surface of the square plate piezoelectric vibrator 20 are arranged.
Although the case where the configuration of 8b is an improved form has been described, the same effect can be obtained by devising and improving the electrode pattern of the internal electrode of the piezoelectric vibrator.

FIG. 3 shows a basic structure of a piezoelectric transformer according to another embodiment of the present invention. FIG. 3 (a) is an exploded perspective view showing a laminated pattern of internal electrodes. FIG. 2B is a perspective view showing the whole appearance, and FIG. 3C is a side sectional view taken along the line AA ′ of FIG. 1B and a partially enlarged view thereof.

The size of each part of this piezoelectric transformer is the same as that of the embodiment, but referring to FIGS. 3A to 3C, a circular internal electrode including a local part extending to the peripheral edge on one corner side. Two
A square thin plate-shaped ceramic sheet made of a piezoelectric ceramic material on which e to 2h are arranged is circular internal electrode 2e to
The input part 32 and the output part 33 are alternately laminated so that the local portions of 2h face each other in a diagonal direction and another diagonal direction perpendicular to the diagonal direction, and the input part 32 and the output part 33 are divided in the stacking direction, and The rectangular plate-shaped piezoelectric vibrator 30 has a laminated structure in which an insulating layer 34 made of a piezoelectric ceramic material is interposed between the input part 32 and the output part 33 in the stacking direction. Input internal electrodes 35 formed by circular internal electrodes 2g and 2h that are exposed in a diagonally opposite direction.
a pair of external electrodes for input 37a, 37 on the local portions of a, 35b
Output by circular internal electrodes 2e, 2f which are arranged so as to extend and connect to the whole of the stacking direction, and which are exposed on the side surface of the rectangular plate-shaped piezoelectric vibrator 30 so as to face each other in a diagonal direction. A pair of output external electrodes 38a, 38b are arranged so as to extend in the entire laminating direction and connect to local portions of the internal electrodes 36a, 36b.

Here, since one of the factors that causes the concentration of the electric field in the piezoelectric vibrator structure is the distance from the external electrode disposed on the side surface to the internal electrode, FIG. 6A is used as a reference. The electric field strength characteristics obtained as a result of the electric field analysis by the finite element analysis when the DC voltage of 5 kV is applied between the input and output terminals of the conventional piezoelectric transformer shown in (c) to the electrode distance (mm ) And electric field strength (V /
mm), the result is as shown in FIG.

From FIG. 4, it is apparent that the electric field strength tends to increase as the distance between the electrodes decreases. Therefore, when the external electrode for connecting to the internal electrode exposed on the side surface is arranged, the circle is previously formed. It is considered that if the diameter of the shaped internal electrode is made small, the distance from the external electrode can be made large and the concentration of the electric field in the piezoelectric vibrator can be reduced.

However, reducing the area of the internal electrodes means reducing the region that contributes to the excitation by the vibration and the extraction of the electric power in the entire piezoelectric vibrator, so that the characteristics of the piezoelectric transformer are significantly reduced. However, it is not preferable to adopt such a configuration only for the reason of reducing the concentration of the electric field.

Therefore, as in the case of the piezoelectric transformer according to another embodiment, the electrode pattern of the internal electrodes is maintained in a circular shape and extends to the peripheral edge of one side of the square thin plate-shaped ceramic sheet without reducing the area. By providing a local portion for connecting the external electrode, it is possible to increase the distance between the external electrode and the internal electrode without deteriorating the basic characteristics of the piezoelectric transformer.

By the way, in the case of a laminated structure type piezoelectric transformer having a square plate shape as a whole, a corner portion which is originally formed by laminating one corner side peripheral edge of a thin plate-like ceramic sheet does not contribute much to the basic characteristics and the internal electrode is Since an unnecessary capacitance is often omitted as a circular shape, the basic characteristics are hardly affected when this corner portion is configured to connect an external electrode for taking out a terminal.

Also in the piezoelectric transformers according to the other embodiments, the two input external electrodes 37a and 37b are short-circuited and the two output external electrodes 38a and 38b are short-circuited so that a direct current is applied between the input and output terminals. The breakdown voltage was examined by applying a voltage, and it was found that the breakdown voltage was 6.0 kV.

FIG. 5 shows a piezoelectric transformer according to another embodiment shown in FIGS. 3A to 3C between input / output terminals connected to an input external electrode and an output external electrode for a converter power supply. The electric field strength distribution obtained as a result of the electric field analysis by the finite element analysis when a DC voltage of 5 kV is applied and used is schematically shown in the figure (a). FIG. 2B is a perspective view including the same, FIG. 2B is a side sectional view including the direction of the electric field in the cutting plane M direction in FIG. 1A, and FIG. The present invention relates to an enlarged view including the directions of the generated electric fields.

From FIGS. 5A to 5C, as a result of the electrolytic analysis, the input external electrodes 37a, 37b and the output external electrode 38 on the peripheral side of the square plate piezoelectric vibrator 30 are obtained.
Although a plurality of arrows indicating the concentration of the electric field in the vicinity of the side surface where a and 38b are arranged are not as great as in the case of the piezoelectric transformer of the embodiment shown in FIGS. 2 (a) to 2 (c). , Fig. 7
Conventional square plate-shaped piezoelectric vibrator 1 shown in (a) to (c)
It is suppressed more than in the case of 0, and a substantially uniform electric field distribution is obtained in the regions E8 and E9 near the insulating layer 34, and a small electric field concentration is obtained in the region E7 in which the insulating layer 34 is close to each external electrode on the side surface. Can be seen.

With respect to the piezoelectric transformer according to the other embodiment, the maximum electric field strength generated by the voltage application and the maximum stress generated by the voltage application were analyzed with a DC voltage of 5 kV applied between the input and output terminals. The maximum electric field strength was 2.8 kV / mm, and the maximum stress was 10 MPa.

As a result, in the case of the piezoelectric transformer according to another embodiment, the maximum electric field strength and the maximum stress are sufficiently improved as compared with the case of the conventional piezoelectric transformer, and the dielectric breakdown does not occur up to 6 kV. It has been found that the basic performance is greatly improved over the conventional piezoelectric transformer even if it is not as high as the piezoelectric transformer, and it is suitable as a step-down piezoelectric transformer for a converter power supply.

In each of the above-mentioned embodiments, the laminated structure type piezoelectric transformer having a square plate shape as a whole has been described. However, it may be configured as a laminated structure type piezoelectric transformer having a rectangular plate shape (rectangular plate shape) as a whole. The present invention is not limited to the embodiment described in each of the embodiments, because substantially the same action and effect can be obtained even in such a case, and the size of each part and the number of layers can be arbitrarily changed.

[0043]

As described above, according to the piezoelectric transformer of the present invention, in the thin plate-shaped ceramic sheet made of the piezoelectric ceramic material, the electrode pattern of the internal electrodes of the rectangular plate-shaped piezoelectric element of the laminated structure is provided for lamination. An existing structure having a circular internal electrode including a local portion extending to one side edge is connected to an input / output internal electrode exposed on a side surface of a rectangular plate piezoelectric element in a laminated state. A thin plate-shaped ceramic sheet is formed by arranging output external electrodes in the region of the input part or output part in the stacking direction, or by improving the electrode pattern of the internal electrodes of a rectangular plate-shaped piezoelectric element of a stacked structure type. In the laminated state, it has a local portion extending to the peripheral edge on one corner side and is used for connecting external electrodes at the corners (for taking out terminals), and is exposed on the side surface of the rectangular plate-shaped piezoelectric element. By arranging the input / output external electrodes connected to the output internal electrodes so as to extend and connect in the entire stacking direction, the dielectric strength (breakdown voltage) and the maximum electric field, which are important as basic characteristics, are set. Since strength and maximum stress can be improved, even if it is used for a converter power supply, local electric field concentration hardly occurs in the piezoelectric vibrator, and breakdown can be prevented with high safety. It is suitable for a converter power supply.

[Brief description of drawings]

1A and 1B show a basic configuration of a piezoelectric transformer according to an embodiment of the present invention, in which FIG. 1A is an external perspective view showing the whole, and FIG. 1B is a side view showing the whole in one direction. Regarding the drawings, (c) relates to a side sectional view in the direction of the line AA 'in (a) and a local enlarged view thereof.

2 is a piezoelectric transformer shown in FIGS. 1 (a) to 1 (c) used as a converter power source by applying a DC voltage of 5 kV between input / output terminals connected to an input external electrode and an output external electrode. A schematic representation of the electric field strength distribution obtained as a result of the electric field analysis by the finite element analysis when
(A) relates to a perspective view including the direction of the electric field on the overall appearance, (b) relates to a side sectional view including the direction of the electric field in the direction of the cutting plane M in (a), (c) (b) ) Relates to an enlarged view including the direction of the electric field in which the local area is enlarged.

3A and 3B show a basic structure of a piezoelectric transformer according to another embodiment of the present invention, in which FIG. 3A is an exploded perspective view showing a laminated pattern of internal electrodes, and FIG. External perspective view, (c) is A-A 'in (b)
The present invention relates to a side sectional view in a line direction and a partially enlarged view thereof.

FIG. 4 shows electric field strength characteristics of a conventional piezoelectric transformer as a function of electric field strength with respect to a distance between electrodes.

5A to 5C are used by applying a DC voltage of 5 kV between the input / output terminals connected to the input external electrode and the output external electrode for the converter power supply using the piezoelectric transformer shown in FIGS. A schematic representation of the electric field strength distribution obtained as a result of the electric field analysis by the finite element analysis when
(A) relates to a perspective view including the direction of the electric field on the overall appearance, (b) relates to a side sectional view including the direction of the electric field in the direction of the cutting plane M in (a), (c) (b) ) Relates to an enlarged view including the direction of the electric field in which the local area is enlarged.

6A and 6B show a basic configuration of a conventional piezoelectric transformer, in which FIG. 6A is an exploded perspective view showing a laminated pattern of internal electrodes, and FIG. 6B is an external perspective view showing the whole. (c) relates to a side sectional view in the direction of the line AA 'in (b) and a local enlarged view thereof.

7A to 7C are used by applying a DC voltage of 5 kV between input / output terminals connected to an input external electrode and an output external electrode for a converter power supply. A schematic representation of the electric field strength distribution obtained as a result of the electric field analysis by the finite element analysis when
(A) relates to a perspective view including the direction of the electric field on the overall appearance, (b) relates to a side sectional view including the direction of the electric field in the direction of the cutting plane M in (a), (c) (b) ) Relates to an enlarged view including the direction of the electric field in which the local area is enlarged.

[Explanation of symbols]

2a to 2h Circular internal electrodes 10, 20, 30 Square plate piezoelectric vibrators 12, 22, 32 Input parts 13, 23, 33 Output parts 14, 24, 34 Insulating parts 15a, 15b, 25a, 25b, 35a, 35b Input internal electrodes 16a, 16b, 26a, 26b, 36a, 36b Output internal electrodes 17a, 17b, 27a, 27b, 37a, 37b Input external electrodes 18a, 18b, 28a, 28b, 38a, 38b Output external electrodes

Claims (2)

[Claims] 1. A rectangular thin plate-shaped ceramic sheet including squares made of a piezoelectric ceramic material, in which a circular internal electrode including a local portion extending to one side edge is disposed, and the local portion of the circular internal electrode is directed in one direction. Direction and the other direction perpendicular to each other on the same plane are alternately laminated to divide the input portion and the output portion in the laminating direction, and the piezoelectric ceramics are provided between the input portion and the output portion. A circular plate-shaped piezoelectric vibrator having a laminated structure in which an insulating layer made of a material is interposed in the stacking direction, and the circular shape that is exposed on the side surface of the rectangular plate-shaped piezoelectric vibrator so as to face the one direction. The pair of input external electrodes are arranged so as to be connected in the local direction of the internal electrodes so as to be connected in the stacking direction, and the circular inside is exposed on the side surface of the rectangular plate piezoelectric vibrator so as to face the other direction. A pair of output external electrodes are attached to the local parts of the electrodes. In the piezoelectric transformer arranged so as to be connected in the layer direction, the pair of input external electrodes are arranged so as to fit within the area of the input unit, and the pair of output external electrodes are arranged in the output unit. A piezoelectric transformer characterized in that it is arranged so as to fit within the area. 2. A rectangular thin plate-shaped ceramic sheet including a square made of a piezoelectric ceramic material, in which a circular internal electrode including a local portion extending to a peripheral edge of one corner is provided, and the local portion of the circular internal electrode is diagonal to the diagonal direction. The input part and the output part are alternately laminated so as to face each other in the diagonal direction which is perpendicular to the other diagonal direction on the same plane, and the input part and the output part are divided in the stacking direction, and the input part and the output part are divided. A rectangular plate-shaped piezoelectric vibrator having a laminated structure in which an insulating layer made of the piezoelectric ceramic material is interposed in the stacking direction, and is provided on a side surface of the rectangular plate-shaped piezoelectric vibrator so as to face each other in the diagonal direction. A pair of input external electrodes are arranged so as to extend and connect to the exposed local portions of the circular internal electrodes in the entire stacking direction, and the pair of external external electrodes are provided on the side surface of the rectangular plate-shaped piezoelectric vibrator and the other pair of electrodes. The circular internal electric charges that are exposed facing each other in the angular direction A piezoelectric transformer, characterized in that a pair of output external electrodes are arranged at local parts of the poles so as to extend and connect to the whole in the stacking direction.