JPH11330580A - Piezoelectric transformer, its manufacture and its driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric transformer suited for the high power use wherein the power resistance is improved with the increase of the safety factor to the breakdown strength and application easiness of the current is improved with the increase of the capacitance. SOLUTION: An input electrode 13, output electrode 14 and common electrode 15 are provided on opposed main planes, and at least two disc-like or ring-like piezoelectric members polarized in the thickness direction are laminated on the main planes and made so as to drive in the radial oscillation mode whereby a piezoelectric transformer suited for the high power use is obtd. wherein the mutually laminated electrodes among the electrodes 13-15 are pref. formed in one body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer, for example, a piezoelectric transformer used in a power converter such as a backlight inverter of a liquid crystal display or a DC-DC converter, a method of manufacturing the piezoelectric transformer, and a method of driving the piezoelectric transformer. It is about.

[0002]

2. Description of the Related Art A piezoelectric transformer converts input electric energy into mechanical energy by an inverse piezoelectric effect, and converts the mechanical energy into electric energy again by a piezoelectric effect, thereby increasing or decreasing a voltage. I have.

[0003] As an example of a piezoelectric transformer, a Rosen type piezoelectric transformer, which is currently the most common configuration, is shown in FIG.
6 is shown. The principle and operation will be described with reference to this Rosen-type piezoelectric transformer. The piezoelectric element is made of a piezoelectric material such as PZT (lead zirconate titanate) ceramic and has a plate shape. This piezoelectric element is constituted by about half each as a drive section 81 and a power generation section 82. The drive unit 81 is provided on the main plane by, for example, silver printing, so that the input electrodes 83
And a common electrode 85, which is polarized in the thickness direction. The power generation section 82 has an output electrode 84 formed on an end face, and is polarized in the long axis direction.

In the piezoelectric transformer thus formed, when an AC electric signal is applied between the input electrode 83 and the common electrode 85, a mechanical vibration is generated by an inverse piezoelectric effect. Due to this mechanical vibration, a stress is applied to the power generation unit 82, and a high voltage is generated between the output electrode 84 and the common electrode 85 by a piezoelectric effect, and is taken out as electric vibration. By setting the applied AC electric signal near the resonance frequency in the long axis direction of the piezoelectric element, a strong mechanical vibration can be obtained.

FIG. 17 shows another proposed type of piezoelectric transformer having a thickness-longitudinal vibration. This piezoelectric transformer is formed by laminating and sintering a piezoelectric body sandwiched between an input electrode 93a, a common electrode 95a, an input electrode 93b, a common electrode 95b, and an output electrode 94. The stacked body from the input electrode 93a to the common electrode 95b forms a piezoelectric body driving unit 91, and the stacked body from the common electrode 95b to the output electrode 94 forms a piezoelectric body power generation unit 92. The piezoelectric body driving section 91 and the piezoelectric body power generation section 92 are polarized in the thickness direction, and the direction of the polarization axis is indicated by an arrow in FIG. This type is driven by vibration in the thickness direction of the piezoelectric body driving section 91 and the piezoelectric body power generation section 92, that is, in the same direction as the polarization direction.

At present, a piezoelectric transformer is often used as an inverter for emitting light from a cold cathode tube as a backlight of a liquid crystal display.
Also considered as a DC converter.

As compared with the electromagnetic transformer, the piezoelectric transformer (1) can be used with a higher power density and is suitable for miniaturization, (2) non-combustibility can be achieved, (3) noise due to electromagnetic induction is reduced, It has the advantage. In the electromagnetic transformer, the power density is improved by increasing the frequency, but the magnetic loss increases with the increase in the frequency, so that the efficiency is reduced.

[0008]

The performance required when a piezoelectric transformer is used for high power applications such as a DC-DC converter is that high power can be easily applied, that is, current can easily flow. For this purpose, it is necessary to lower the input impedance of the piezoelectric transformer (= increase the input capacitance). In the case of a DC-DC converter, it is necessary to lower the output impedance. In addition, the piezoelectric transformer is required to have a property of being resistant to destruction even when a large power is applied and having high power durability. Since the conventional Rosen-type piezoelectric transformer has a main purpose of boosting the voltage, the capacity of the output unit cannot be increased, and a large amount of current cannot be taken out. In addition, since there is a boundary layer of the polarization axis at the boundary between the driving unit and the power generation unit, it is easily broken and has low power durability.

In addition, when used in a DC-DC converter, increasing the driving frequency causes a problem that the efficiency of components used in the DC-DC converter such as a switch diode, a coil, and a control circuit is reduced.

The conventional piezoelectric transformer of thickness longitudinal vibration shown in FIG. 17 has a piezoelectric driving portion 91 and a piezoelectric power generating portion 9 on a main plane.
By laminating 2 and 2, the capacity of the output section can be increased, but the vibration is determined by the thickness, so the thickness of the entire main plane is not uniform, and the frequency is high, and other higher-order vibrations However, there are problems such as easy excitation (in other words, unnecessary vibration is generated), and the transmitted vibration waveform is disturbed, and the reliability as a transformer is not sufficient. In addition, since the vibration in the thickness direction has a high frequency, the loss in the related parts is large, and there is a problem that the efficiency of the entire device is reduced when the present piezoelectric transformer is used.

In view of the above-mentioned problems of the conventional piezoelectric transformer, the present invention improves the power durability by increasing the safety factor against the breaking strength, and improves the ease of applying a current by increasing the capacitance. Piezoelectric transformer suitable for high power,
It is an object of the present invention to provide a method for manufacturing a piezoelectric transformer and a method for driving a piezoelectric transformer.

[0012]

Means for Solving the Problems In order to solve the above-mentioned problems, a first present invention (corresponding to the first aspect of the present invention).
Comprises at least two or more piezoelectric bodies polarized in the thickness direction and having electrodes on opposing main planes, wherein the piezoelectric bodies are superimposed on each other on the main plane, and are driven in a spreading vibration mode. A piezoelectric transformer characterized in that: Thus, input / output electrodes can be formed over the entire main plane, and the capacitance can be increased. In addition, it is possible to prevent the use frequency from increasing. Also,
It is possible to increase the safety factor against the breaking strength.

According to a second aspect of the present invention (corresponding to the second aspect of the present invention), in the first aspect, the electrodes overlapping each other are integrally formed.
Of the present invention. As a result, the electrodes can be shared as a common electrode, so that the manufacturing cost can be reduced.

According to a third aspect of the present invention (corresponding to the third aspect of the present invention), the piezoelectric transformer according to the first aspect of the present invention is characterized in that the piezoelectric bodies are superposed via an insulating layer. is there. As a result, the drive unit and the power generation unit can be used in a state where they are electrically separated, and the output current can be easily taken out.
It becomes easy to use for a C-DC converter.

A fourth aspect of the present invention (corresponding to the fourth aspect of the present invention) is characterized in that the insulating layer is made of any one of the same material as the adhesive, ceramic, and piezoelectric material and is unpolarized. The third aspect of the present invention is a piezoelectric transformer according to the present invention. When the insulating layer is made of an adhesive, superposition and electrical separation of the power generation unit and the drive unit can be performed simultaneously. When the insulating layer is made of ceramic, it can be integrally fired, and the production becomes easy.
When the insulating layer is made of the same material as that of the piezoelectric body and is not polarized, characteristics such as thermal expansion of the piezoelectric body can be made the same.

According to a fifth aspect of the present invention (corresponding to the fifth aspect of the present invention), at least one of the piezoelectric bodies has one of the electrodes on the main plane on the opposite side via a side surface of the piezoelectric body. The piezoelectric transformer according to any one of the first to fourth aspects of the present invention, wherein the piezoelectric transformer is formed up to the main plane. Thus, the electrodes can be drawn out from the main plane, not from the side surface that is the vibration direction, so that the manufacturing is facilitated and the piezoelectric transformer is easily fixed.

A sixth aspect of the present invention (corresponding to the sixth aspect of the present invention) comprises a piezoelectric body polarized in a thickness direction and having an input electrode and an output electrode on opposing main planes,
Either the input electrode or the output electrode,
A piezoelectric transformer is disposed substantially at the center of the main plane, and the other is disposed so as to surround the one, and is driven in a spread vibration mode. Thereby, the piezoelectric transformer can be manufactured with a simpler configuration.

A seventh aspect of the present invention (corresponding to the seventh aspect of the present invention) is the piezoelectric transformer according to the sixth aspect of the present invention, which is driven in a spread vibration mode. This allows
It is possible to prevent the use frequency from rising. Also, it is possible to increase the safety factor against the breaking strength.

According to an eighth aspect of the present invention (corresponding to the eighth aspect of the present invention), the shape of the main plane is substantially similar to the polygon from a circle, ring, polygon, or polygon. The piezoelectric transformer according to any one of the first to seventh aspects of the present invention, which is one of a figure obtained by punching a figure. By making the shape of the main plane substantially a circle or a ring, an efficient piezoelectric transformer can be provided. Further, by making the shape into a polygon or a figure obtained by punching out a figure similar to the polygon from the polygon, in particular, a square or a regular hexagon, the processing by cutting becomes easy, and the productivity is improved.

A ninth aspect of the present invention (corresponding to the ninth aspect of the present invention) is the piezoelectric transformer according to any one of the first to eighth aspects, wherein the piezoelectric body is a piezoelectric ceramic. It is. Thus, an inexpensive piezoelectric transformer having a large piezoelectric constant can be provided.

According to a tenth aspect of the present invention (corresponding to the tenth aspect of the present invention), in a method of manufacturing a piezoelectric transformer driven in a spread vibration mode, a polarizing step of polarizing a piezoelectric body in a thickness direction; After the step, a laminating step of laminating at least two or more of the piezoelectric bodies so that their main planes are overlapped with each other. As a result, a piezoelectric transformer can be manufactured even with a piezoelectric material that has good piezoelectric characteristics and strength characteristics but has a high sintering temperature and cannot be used with a green sheet lamination method.

According to an eleventh aspect of the present invention (corresponding to the eleventh aspect of the present invention), in a method of manufacturing a piezoelectric transformer driven in a spread vibration mode, at least two or more piezoelectric bodies are overlapped on their main planes. A method for manufacturing a piezoelectric transformer, comprising: a laminating step of laminating so as to be combined with each other; and a sintering step of sintering the piezoelectric body after the laminating step. This facilitates the lamination of the piezoelectric body driving unit or the piezoelectric body power generation unit, and makes it easy to increase the capacitance.

A twelfth aspect of the present invention (corresponding to the twelfth aspect of the present invention) comprises at least two or more piezoelectric bodies which are polarized in the thickness direction and have electrodes on opposing main planes, respectively. A driving method of a piezoelectric transformer, wherein a piezoelectric transformer whose bodies are overlapped on the main plane is driven in a spread vibration mode. As a result, it is possible to prevent the use frequency from increasing. Also, it is possible to increase the safety factor against the breaking strength.

A thirteenth aspect of the present invention (corresponding to the thirteenth aspect of the present invention) comprises a piezoelectric body polarized in the thickness direction and having an input electrode and an output electrode on opposing main planes, respectively. One of the output electrodes is disposed substantially at the center of the main plane, and the other drives a piezoelectric transformer disposed to surround the one in a spread vibration mode. Is a driving method of the piezoelectric transformer. As a result, it is possible to prevent the use frequency from increasing. Also, it is possible to increase the safety factor against the breaking strength.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) First, the first embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings.

FIG. 1 is an external view showing a piezoelectric transformer according to a first embodiment of the present invention. The piezoelectric body used in the piezoelectric transformer according to the present embodiment is a PZT-based ceramic, which is sintered into a disk shape and then polished, and the piezoelectric body driving unit 11 is φ16 mm, has a thickness of 0.25 mm, and has a piezoelectric power generation. The part 12 has an outer size of φ16 mm and a thickness of 0.75 mm. Furthermore, on each main plane,
An electrode is formed by evaporating chromium-gold and polarized in the thickness direction. Arrows in FIG. 1 indicate the directions of the polarization axes. The piezoelectric body driving section 11 and the piezoelectric body power generation section 1
When 2 is laminated on the main plane using a conductive adhesive, the overall outer shape of the piezoelectric transformer is φ16 mm and the thickness is 1 mm.
The electrodes on the laminated surface are electrically connected by a conductive adhesive, and are used as common electrodes 15. The electrodes other than the common electrode 15 are an input electrode 13 and an output electrode 14, respectively, of the piezoelectric body driving unit 11 and the piezoelectric body power generation unit 12. Input electrode 1
3. The conductive adhesive is also used for taking out the lead wire from the output electrode 14 and the common electrode 15. The piezoelectric transformer thus obtained is driven by the radially expanding vibration of the disk,
The resonance frequency is about 145 kHz.

As described in the background art, the piezoelectric transformer has a configuration in which an electric signal is input, converted into mechanical vibration by a drive unit, converted into an electric signal again by a power generation unit, and stepped up and down. Therefore, the conventional Rosen type transformer, thickness vertical type transformer, and disk type transformer have a configuration in which the power generation unit is provided in the vibration direction of the drive unit and the vibration is propagated. In the present embodiment, the configuration is such that the radial vibration of the drive unit is propagated not as the vibration direction but as a surface to the power generation unit by laminating on the main plane. Further, since the radial vibration is a vibration perpendicular to the polarization axis, it is possible to suppress a decrease in piezoelectric characteristics and the like against a large vibration when a large power is applied.

For comparison, a conventional Rosen-type piezoelectric transformer was manufactured to have the same volume and a length of 20 mm, a width of 10 mm, and a thickness of 1 mm. The drive section 81 is polarized in the thickness direction, and the power generation section 82 is polarized in the long axis direction. The input electrode 83, the output electrode 84, and the common electrode 85 were formed by evaporating chromium-gold. The Rosen-type transformer is driven in the λ mode of elongational vibration in the major axis direction, and has a resonance frequency of 150 kHz.

The capacitance of the conventional Rosen-type piezoelectric transformer is 1 nF for the input section and 0.12 F for the output section. However, this transformer can use the entire area of the input section and the output section, and the input section 8 nF.
F, it was confirmed that the output portion was significantly increased to 2.7 nF.

FIG. 2 shows the frequency characteristics of the efficiency when a load resistance of 1 kΩ is applied between the output electrode 14 and the common electrode 15. At a resonance frequency of 145 kHz, the efficiency was 96% and the step-down ratio was 1/2.

In order to check the safety factor against the breaking strength,
Driven at the resonance frequency, the applied power was increased, and the vibration speed was increased until the piezoelectric transformer was destroyed. When the applied power became 19 W, the Rosen transformer was broken at the center of the output section. This piezoelectric transformer did not break even when 50 W was applied, and it was confirmed that the withstand power was able to be increased about 2.5 times or more. The reason that the Rosen-type piezoelectric transformer is broken at the center of the output unit is that, in the λ mode, the center of the input / output unit of the piezoelectric body is the point of maximum stress. In this transformer, the stress in the central portion is the highest, but since it is a mode that expands in the radial direction, the stress is dispersed as compared with the Rosen type, and the transformer has not been destroyed.

In this embodiment, a PZT-based ceramic is used as the piezoelectric material. However, the same effect can be obtained by using a piezoelectric material, for example, a piezoelectric single crystal of LiNo3.

In this embodiment, the electrodes are formed on the entire surface of the main surface of the piezoelectric body. However, the same effect can be obtained by forming the electrodes on a part of the main surface.

In this embodiment, the layers are stacked with the polarization axes in the same direction. However, similar effects can be obtained by stacking in the opposite direction.

In the present embodiment, the piezoelectric body driving section and the piezoelectric body power generation section are formed in a disk shape. However, one or both of the piezoelectric body driving section and the piezoelectric body power generation section are connected to a ring. The same effect can be obtained because the shape can be driven by radial vibration.

In the present embodiment, the piezoelectric transformer is used for step-down, but the same effect can be obtained even if the piezoelectric transformer is designed for step-up.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings. The piezoelectric transformer according to the present embodiment is the same as the piezoelectric transformer according to the above-described first embodiment except for the planar shape and the polarization direction. Therefore, in the present embodiment, components that are not particularly described are assumed to be the same as those in the first embodiment, and the components having the same names as those in the first embodiment will be the same as those in the first embodiment unless otherwise described. It has the same function as the embodiment.

FIG. 3 is an external view showing a piezoelectric transformer according to a second embodiment of the present invention. The piezoelectric body used for the piezoelectric transformer in the present embodiment is a PZT-based ceramic, and after sintering, cutting and polishing into a square shape,
The piezoelectric body drive unit 21 is 14 mm square, 0.25 mm thick,
The piezoelectric power generation section 22 has an outer size of 14 mm square and 0.75 mm thickness. The polarization, electrodes, lamination, and the like are the same as those of the piezoelectric transformer in the first embodiment, and constitute the input electrode 23, the output electrode 24, and the common electrode 25. The overall outer shape of the piezoelectric transformer is 14 mm square and 1 mm thick. is there.
The volume is almost the same as the piezoelectric transformer in the first embodiment. The thus obtained piezoelectric transformer is driven by spread vibration, and has a resonance frequency of about 165 kHz.

In the present piezoelectric transformer, the capacitance is 8 nF at the input part and 2.7 nF at the output part, and can be greatly increased as compared with the Rosen-type transformer like the piezoelectric transformer in the first embodiment. It was confirmed that.

FIG. 4 shows the frequency characteristics of the efficiency when a load resistance of 1 kΩ is applied between the output electrode 24 and the common electrode 25. At a resonance frequency of 165 kHz, the efficiency was 92% and the step-down ratio was about 1/2 times.

In order to examine the safety factor for the breaking strength,
Driven at the resonance frequency, the applied power was increased, and the vibration speed was increased. However, this piezoelectric transformer did not break even when 50 W was applied, and it was confirmed that the withstand power could be increased to about 2.5 times or more as compared with the Rosen type piezoelectric transformer.

(Third Embodiment) Next, a third embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings. The piezoelectric transformer according to the present embodiment is the same as the piezoelectric transformer according to the above-described first embodiment except that the piezoelectric transformer is overlapped with an insulating layer interposed therebetween. Therefore, in this embodiment, unless otherwise specified,
The same components as those of the first embodiment are designated by the same reference numerals as those of the first embodiment, unless otherwise specified.
It has the same function as that of the embodiment.

FIG. 5 is an external view showing a piezoelectric transformer according to a third embodiment of the present invention. The piezoelectric body used in the piezoelectric transformer according to the present embodiment is a PZT-based ceramic, which is polished after sintering into a disc shape, and the piezoelectric body driving unit 31 has a diameter of 16 mm, a thickness of 0.25 mm, and a piezoelectric power generation. The portion 32 has an outer size of φ16 mm and a thickness of 0.75 mm. Furthermore, on each main plane,
An electrode is formed by depositing chromium-gold, and is polarized in the thickness direction. Arrows in FIG. 5 indicate the directions of the polarization axes. In addition, the same ceramic as the insulating layer 35 has a diameter of φ1.
6 mm and a thickness of 0.1 mm are also formed. The insulating layer 35 is not polarized. When the piezoelectric driving unit 31, the piezoelectric power generating unit 32, and the insulating layer 35 are laminated on the main plane using an insulating adhesive, the overall outer shape of the piezoelectric transformer is φ16 mm and the thickness is 1.1 mm.
The electrodes of the piezoelectric body driving unit 31 and the piezoelectric body power generation unit 32 are input electrodes 33a and 33b and output electrodes 34a and 34b, respectively. The lead wire is taken out from each electrode using a conductive adhesive. The thus obtained piezoelectric transformer is driven by the radially expanding vibration of the disk, and has a resonance frequency of about 145 kHz.

In the present piezoelectric transformer, the piezoelectric driving unit 3
By laminating the piezoelectric element 1 and the piezoelectric power generating section 32 with an insulating layer 35 interposed therebetween, it can be used in a state where the potential between the input voltage and the output voltage is separated.

In the present piezoelectric transformer, the capacitance is 8 nF at the input part and 2.7 nF at the output part, which is much larger than that of the Rosen-type transformer like the piezoelectric transformer in the first embodiment. confirmed.

FIG. 3 shows the frequency characteristics of the efficiency when a load resistance of 1 kΩ is applied between the output electrode 24 and the common electrode 25. At a resonance frequency of 145 kHz, the efficiency was 92% and the step-down ratio was about 1/2 times.

In order to examine the safety factor for the breaking strength,
Driven at the resonance frequency, the applied power was increased, and the vibration speed was increased. However, this piezoelectric transformer did not break even when 50 W was applied, and it was confirmed that the withstand power could be increased to about 2.5 times or more as compared with the Rosen type piezoelectric transformer.

In this embodiment, the insulating layer is made of ceramic. However, the same effect can be obtained as long as the insulating property is maintained by a non-conductive adhesive or the like.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings. The piezoelectric transformer according to the present embodiment is the same as the piezoelectric transformer according to the above-described first embodiment, except that only one piezoelectric body having an input electrode and an output electrode is provided on the opposing main plane. is there. Therefore, in the present embodiment, those not particularly described are the same as those in the first embodiment.
The components having the same names as those of the first embodiment have the same functions as those of the first embodiment unless otherwise specified.

FIG. 7 is an external view of a piezoelectric transformer according to a fourth embodiment of the present invention, and FIG. 8 is a central cross-sectional view thereof.
The piezoelectric body produced in the present embodiment is a PZT-based ceramic, which is sintered into a disc shape, polished,
mm and a thickness of 1 mm. Further, electrodes were formed by depositing chromium-gold on the entire surfaces on both main planes, and were polarized in the thickness direction. After that, the electrodes on both main planes have an inner diameter of 8.5 mm and an outer diameter of 1 mm.
Drop the electrode of the 0.5 mm ring part and set the inside diameter φ10.
5, a ring-shaped electrode having an outer diameter of φ16 mm is connected to the input electrode 43a,
b, φ8.5 mm circular electrodes are output electrodes 44a, b. In other words, the portion sandwiched between the input electrodes 43a and 43b becomes the piezoelectric driving unit 41, and the portion sandwiched between the output electrodes 44a and 44b becomes the piezoelectric power generating unit 42. Arrows in FIG. 7 indicate the directions of the polarization axes. The lead wire is taken out from each electrode using a conductive adhesive. The piezoelectric transformer thus obtained is driven by the radially expanding vibration of the disk, and the resonance frequency is determined by the external dimensions, and is approximately 145 kHz.
It is.

In the present piezoelectric transformer, it was confirmed that the capacitance could be increased by 3.5 nF in the input section and 1.7 nF in the output section as in the Rosen type transformer as in the first embodiment.

FIG. 9 shows the frequency characteristics of the efficiency when a load resistance of 1.6 kΩ is applied between the output electrodes 44a and 44b. At a resonance frequency of 145 kHz, the efficiency was 94% and the step-down ratio was about 1/2 times.

In order to check the safety factor for the breaking strength,
Driven at the resonance frequency, the applied power was increased, and the vibration speed was increased. However, this piezoelectric transformer did not break even when 50 W was applied, and it was confirmed that the withstand power could be increased to about 2.5 times or more as compared with the Rosen type piezoelectric transformer.

In the present embodiment, the driving is performed by the radially expanding vibration. However, as long as the vibration is transmitted from the driving unit to the power generation unit, the driving by the same piezoelectric body is possible even in the case of the thickness vertical vibration. Since the power generation is performed, the disturbance of the vibration waveform unlike the conventional piezoelectric transformer of the thickness longitudinal vibration does not occur,
The effect of improving the reliability as a transformer is obtained.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings. The piezoelectric transformer according to the present embodiment is the same as the piezoelectric transformer according to the above-described first embodiment except for the configuration of the electrodes and the polarization direction. Therefore, in the present embodiment, components that are not particularly described are assumed to be the same as those in the first embodiment, and the components having the same names as those in the first embodiment will be the same as those in the first embodiment unless otherwise described. It has the same function as the embodiment.

FIG. 10 is an external view showing a piezoelectric transformer according to a fifth embodiment of the present invention. The piezoelectric body used for the piezoelectric transformer in the present embodiment is a PZT-based ceramic, which is sintered into a disc shape, polished,
The outer diameter is 6 mm and the thickness is 1 mm. Further, electrodes are formed by depositing chromium-gold on the entire surface on both main planes, and are polarized in the thickness direction.
The piezoelectric body driving section 51 has a diameter of 16 mm, a thickness of 0.25 mm,
The piezoelectric power generation section 52 has an outer size of φ16 mm and a thickness of 0.75 mm. Arrows in FIG. 10 indicate the directions of the polarization axes. After the polarization, the electrodes on one side of both the piezoelectric body driving unit 51 and the piezoelectric body power generation unit 52 were dropped, and φ was newly added to the center.
A ring-shaped electrode having electrical conduction is formed through thirteen circular electrodes and the opposite main plane and side surfaces. The piezoelectric body driving section 51 and the piezoelectric body power generation section 52 are laminated on the main plane using a conductive adhesive, and the circular electrode of the piezoelectric body driving section 51 is used as the input electrode 53 and the circular electrode of the piezoelectric body power generation section 52 is used as the output. Electrode 5
4, and the electrode led out through the side surface is used as the common electrode 55. The lead wire is taken out from each electrode using a conductive adhesive. The piezoelectric transformer thus obtained is driven by the radially expanding vibration of the disk, and the resonance frequency is determined by the external dimensions, and is about 145 kHz.

In the present piezoelectric transformer, by taking out the common electrode 55 on the main plane, it is easy to take out the electrode, and it is easy to mount the piezoelectric transformer.

In the present piezoelectric transformer, the capacitance can be greatly increased as compared with the Rosen type transformer like the piezoelectric transformer in the first embodiment with the input part 6.5 nF and the output part 2.2 F. It was confirmed that.

1.2 k between output electrode 54 and common electrode 55
Fig. 11 shows the frequency characteristics of efficiency when a load resistance of Ω is applied.
Shown in When the resonance frequency is 145 kHz, the efficiency is 94%,
The step-down ratio was about 1/2.

In order to check the safety factor for the breaking strength,
Driven at the resonance frequency, the applied power was increased, and the vibration speed was increased. However, this piezoelectric transformer did not break even when 50 W was applied, and it was confirmed that the withstand power could be increased to about 2.5 times or more as compared with the Rosen type piezoelectric transformer.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings. The piezoelectric transformer according to the present embodiment is the same as the piezoelectric transformer according to the above-described first embodiment except for the number of stacked piezoelectric bodies and the polarization direction. Therefore, in the present embodiment, components that are not particularly described are assumed to be the same as those in the first embodiment, and the components having the same names as those in the first embodiment will be the same as those in the first embodiment unless otherwise described. It has the same function as the embodiment.

FIG. 12 is an external view showing a piezoelectric transformer according to a sixth embodiment of the present invention. The piezoelectric body used in the piezoelectric transformer in the present embodiment is a PZT-based ceramic, and a green sheet having a thickness of about 30 μm is formed by a doctor blade method, and the output electrode 64, the common electrode 65a, After b. is formed of a silver / palladium paste, the drive units 61a and 61b are laminated in three layers, and the power generation unit 62 is laminated in 15 layers. Thereafter, the input electrodes 63a and 63b are provided by polishing and silver baking. The external dimensions after sintering are φ16 mm and thickness 1 mm. After the electrodes are formed, both the driving section and the power generation section are polarized in the thickness direction. Arrows in FIG. 12 indicate polarization directions. The lead wires are taken out of the input electrodes 63a, b, the output electrode 64, and the common electrodes 65a, b with a conductive adhesive, and the lead wires are connected between the input electrodes 63a, b and between the common electrodes 65a, b. Has continuity.

The resonance frequency is in the radially expanding vibration mode, similar to the piezoelectric transformer in the first embodiment, and the resonance frequency is about 145 kHz.

The capacitance is considerably larger than that of the conventional Rosen-type piezoelectric transformer, with the driving part 33 nF and the output part 8.5 nF, because the piezoelectric driving part is thin and the number of layers is also two. FIG. 13 shows the frequency characteristics of the efficiency when a load resistance of 500Ω is applied between the output electrode 64 and the common electrodes 65a and 65b. When the resonance frequency is 145 kHz, the efficiency is 9
4% and the step-down ratio was 1/2 times.

In order to examine the safety factor for the breaking strength,
Driven at the resonance frequency, the applied power was increased, and the vibration speed was increased. However, this piezoelectric transformer did not break even when 50 W was applied, and it was confirmed that the withstand power could be increased to about 2.5 times or more as compared with the Rosen type piezoelectric transformer.

(Seventh Embodiment) Next, a seventh embodiment of the present invention will be described.
An embodiment will be described with reference to the drawings. The piezoelectric transformer according to the present embodiment is the same as the piezoelectric transformer according to the above-described second embodiment except for the number of stacked piezoelectric bodies. Therefore, in the present embodiment,
Unless otherwise described, the same components as those of the second embodiment are assumed to have the same functions as those of the second embodiment unless otherwise specified. Shall have.

FIG. 14 is an external view showing a piezoelectric transformer according to a seventh embodiment of the present invention. The piezoelectric body used for the piezoelectric transformer in the present embodiment is a PZT-based ceramic, a green sheet having a thickness of about 30 μm is formed by a doctor blade method, and the output electrode 74, the common electrode 75a, After b. is formed of silver / palladium paste, the drive units 71a and b are laminated in three layers, and the power generation unit 72 is laminated in 15 layers, pressed and sintered, then polished on the main surface, and baked on the input electrode by silver baking. 73a, b
Is formed. After the electrodes are formed, both the drive unit and the power generation unit are polarized in the thickness direction.
Of square shape and 1 mm in thickness.
By making the shape square, the shape can be determined by cutting, and the productivity is improved. Arrows in FIG. 14 indicate the polarization direction. The lead wires from the input electrodes 73a and 73b, the output electrode 74, and the common electrodes 75a and 75b are taken out using a conductive adhesive, and between the input electrodes 73a and 73b and between the common electrodes 75a and 75b.
Conductivity is provided by connecting the lead wires between b.

The resonance frequency is the spread vibration mode, as in the piezoelectric transformer in the second embodiment, and the resonance frequency is about 165 kHz.

Since the capacitance of the piezoelectric driving section is thin and the number of layers is also two, the capacitance is considerably larger than that of the conventional Rosen-type piezoelectric transformer with a driving section of 33 nF and an output section of 8.5 nF. FIG. 15 shows the frequency characteristics of the efficiency when a load resistance of 500Ω is applied between the output electrode 74 and the common electrodes 75a and 75b. When the resonance frequency is 165 kHz, the efficiency is 9
0% and the step-down ratio was 1/2 times.

In order to examine the safety factor for the breaking strength,
Driven at the resonance frequency, the applied power was increased, and the vibration speed was increased. However, this piezoelectric transformer did not break even when 50 W was applied, and it was confirmed that the withstand power could be increased to about 2.5 times or more as compared with the Rosen type piezoelectric transformer.

In the first to seventh embodiments described above, the shape of the main plane and the electrode has been described as being substantially any of a circle, a ring, and a square. However, the present invention is not limited to this. Rather, for example, a polygon, or a figure obtained by punching out a figure similar to the polygon from a polygon, although there is a quantitative difference in the effect, compared to a conventional piezoelectric transformer, The capacity can be increased, and the effect of preventing the use frequency from increasing can be obtained.

In the first to seventh embodiments, the piezoelectric transformer of the present invention and the method of manufacturing the piezoelectric transformer have been mainly described. However, the driving method of the piezoelectric transformer of the present invention This is a driving method of a piezoelectric transformer that drives a piezoelectric transformer having the same configuration as the piezoelectric transformer in a spread vibration mode.

[0074]

As is apparent from the above description, the present invention improves the power durability by increasing the safety factor against the breaking strength, and improves the ease of applying a current by increasing the capacitance. A piezoelectric transformer suitable for electric power, a method for manufacturing the piezoelectric transformer, and a method for driving the piezoelectric transformer can be provided.

That is, according to the first aspect of the present invention, the input / output electrodes can be formed on the entire main plane, the capacitance can be increased, and the use frequency can be prevented from increasing. Further, it is possible to provide a piezoelectric transformer capable of increasing the safety factor against the breaking strength.

According to the second aspect of the present invention, it is possible to provide a piezoelectric transformer capable of reducing the manufacturing cost by sharing the electrode as a common electrode.

According to the third aspect of the present invention, it is possible to provide a piezoelectric transformer which can be used in a state in which the drive unit and the power generation unit are electrically separated, and which can easily take out an output current and be easily used in a DC-DC converter. .

According to the fourth aspect of the present invention, the superposition and the electrical separation of the power generation section and the drive section can be simultaneously performed by using the insulating layer as an adhesive, and the insulating layer can be integrally fired by using a ceramic. By making the insulating layer unpolarized with the same material as that of the piezoelectric body, it is possible to provide a piezoelectric transformer having the same characteristics as the piezoelectric body such as thermal expansion.

According to the fifth aspect of the present invention, it is possible to provide a piezoelectric transformer that can be easily manufactured and can be easily fixed because the electrodes can be pulled out from the main plane, not from the side surface in the vibration direction. .

The present invention according to claim 6 can provide a piezoelectric transformer that can be manufactured with a simpler configuration.

According to the seventh aspect of the present invention, it is possible to prevent the use frequency from increasing. Further, it is possible to provide a piezoelectric transformer capable of increasing the safety factor against the breaking strength.

The present invention according to claim 8 can provide a piezoelectric transformer with high efficiency or a piezoelectric transformer with improved productivity.

According to the ninth aspect of the present invention, the piezoelectric constant is large,
An inexpensive piezoelectric transformer can be provided.

According to a tenth aspect of the present invention, there is provided a method of manufacturing a piezoelectric transformer capable of manufacturing a piezoelectric transformer even in a piezoelectric material having a high sintering temperature and a green sheet laminating method cannot be used, although the piezoelectric characteristics and strength characteristics are good. Can be provided.

According to the eleventh aspect of the present invention, it is possible to provide a method of manufacturing a piezoelectric transformer in which a piezoelectric driving unit or a piezoelectric power generating unit can be easily laminated and the capacitance can be easily increased.

According to the twelfth aspect of the present invention, it is possible to prevent the use frequency from increasing. Further, it is possible to provide a driving method of a piezoelectric transformer that can increase a safety factor with respect to breaking strength.

According to the thirteenth aspect of the present invention, it is possible to prevent the use frequency from increasing. Further, it is possible to provide a driving method of a piezoelectric transformer that can increase a safety factor with respect to breaking strength.

[Brief description of the drawings]

FIG. 1 is an external view showing a piezoelectric transformer according to a first embodiment of the present invention.

FIG. 2 is a frequency characteristic diagram of the efficiency of the piezoelectric transformer according to the first embodiment of the present invention.

FIG. 3 is an external view of a piezoelectric transformer according to a second embodiment of the present invention.

FIG. 4 is a frequency characteristic diagram of the efficiency of a piezoelectric transformer according to a second embodiment of the present invention.

FIG. 5 is an external view of a piezoelectric transformer according to a third embodiment of the present invention.

FIG. 6 is a frequency characteristic diagram of the efficiency of a piezoelectric transformer according to a third embodiment of the present invention.

FIG. 7 is an external view of a piezoelectric transformer according to a fourth embodiment of the present invention.

FIG. 8 is a central cross-sectional view of a piezoelectric transformer according to a fourth embodiment of the present invention.

FIG. 9 is a frequency characteristic diagram of the efficiency of a piezoelectric transformer according to a fourth embodiment of the present invention.

FIG. 10 is an external view of a piezoelectric transformer according to a fifth embodiment of the present invention.

FIG. 11 is a frequency characteristic diagram of the efficiency of a piezoelectric transformer according to a fifth embodiment of the present invention.

FIG. 12 is an external view of a piezoelectric transformer according to a sixth embodiment of the present invention.

FIG. 13 is a frequency characteristic diagram of the efficiency of a piezoelectric transformer according to a sixth embodiment of the present invention.

FIG. 14 is an external view of a piezoelectric transformer according to a seventh embodiment of the present invention.

FIG. 15 is a frequency characteristic diagram of the efficiency of a piezoelectric transformer according to a seventh embodiment of the present invention.

FIG. 16 is an external view of a conventional Rosen-type piezoelectric transformer.

FIG. 17 is an external view of a conventional disk-type piezoelectric transformer.

[Explanation of symbols]

11, 21, 31, 41, 51, 61, 71, 81, 9
DESCRIPTION OF SYMBOLS 1 Piezoelectric body drive part 12, 22, 32, 42, 52, 62, 72, 82, 9
2 Piezoelectric power generation unit 13, 23, 33, 43, 53, 63, 73, 83, 9
3 input electrodes 14, 24, 34, 44, 54, 64, 74, 84, 9
4 output electrode 15, 25, 55, 65, 75, 85, 95 common electrode 35 insulating layer

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hiroyuki Hase 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd.

Claims (13)

[Claims] 1. At least two or more piezoelectric bodies polarized in a thickness direction and each having an electrode on an opposing main plane, wherein the piezoelectric bodies are overlapped with each other on the main plane, and in a spread vibration mode. A piezoelectric transformer characterized by being driven. 2. The piezoelectric transformer according to claim 1, wherein, among the electrodes, those overlapping each other are integrally formed. 3. The piezoelectric transformer according to claim 1, wherein the piezoelectric bodies are overlapped via an insulating layer. 4. The piezoelectric transformer according to claim 3, wherein the insulating layer is made of one of an adhesive, ceramic, and the same material as the piezoelectric body and is unpolarized. 5. At least one of the piezoelectric bodies is characterized in that the electrode on one of the main planes is formed on the opposite main plane via a side surface of the piezoelectric body. The piezoelectric transformer according to claim 1. 6. A piezoelectric body polarized in a thickness direction and having an input electrode and an output electrode on opposing main planes, wherein one of the input electrode and the output electrode is substantially the main electrode. A piezoelectric transformer, wherein the piezoelectric transformer is arranged at the center of a plane, and the other is arranged so as to surround the one. 7. The piezoelectric transformer according to claim 6, wherein the piezoelectric transformer is driven in a spread vibration mode. 8. The shape of the main plane is substantially any one of a circle, a ring, a polygon, and a figure obtained by stamping a figure similar to the polygon from a polygon. 8. The piezoelectric transformer according to any one of 1 to 7. 9. The piezoelectric transformer according to claim 1, wherein the piezoelectric body is a piezoelectric ceramic. 10. A method of manufacturing a piezoelectric transformer driven in a spread vibration mode, wherein: a polarization step of polarizing a piezoelectric body in a thickness direction; and after the polarization step, at least two or more piezoelectric bodies are separated from each other by main planes. And a laminating step of laminating the piezoelectric transformers so as to overlap each other. 11. A method for manufacturing a piezoelectric transformer driven in a spread vibration mode, wherein: a laminating step of laminating at least two or more piezoelectric bodies such that their main planes are superimposed on each other; A sintering step of sintering the piezoelectric transformer. 12. A piezoelectric transformer comprising at least two or more piezoelectric bodies polarized in a thickness direction and having electrodes on opposing main planes, wherein the piezoelectric bodies are superposed on each other on the main plane. A method for driving a piezoelectric transformer, characterized by driving in a vibration mode. 13. A piezoelectric body polarized in a thickness direction and having an input electrode and an output electrode on opposing main planes, wherein one of the input electrode and the output electrode is substantially the main electrode. Placed in the center of the plane, the other
A method for driving a piezoelectric transformer, comprising: driving a piezoelectric transformer disposed so as to surround the one side in a spread vibration mode.