JP3405033B2 - Piezoelectric transformer - Google Patents

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 converting an amplitude value of an AC voltage by a piezoelectric effect of a piezoelectric body such as a piezoelectric ceramic.

[0002]

2. Description of the Related Art Piezoelectric transformers developed in the late 1950's were focused on as step-up transformers for high-voltage power supplies and were developed. However, due to material restrictions such as breaking strength of piezoelectric ceramic materials, they were made into a large product. Development was suspended without being done. However, with the recent development of high-strength piezoelectric ceramics, the demand for smaller and thinner portable information devices such as notebook computers, electronic organizers, and game consoles has become stronger. It is receiving a great deal of attention again as a step-up transformer for an inverter power supply for lights.

For example, an inverter for a liquid crystal backlight is used as a lighting power source for a cold cathode fluorescent lamp used as a light source for a backlight, and is composed of a battery or the like.
It is necessary to convert a low DC voltage such as V, 5V, 9V, 12V into a high frequency high voltage of about 1000 Vrms during lighting and about 500 Vrms during steady state. At present, the electromagnetic winding transformer used in the backlight inverter has been made thinner by using a horizontal structure transformer with a special core. There is a limit, and there is a drawback that core loss and winding loss due to the use of a thin copper wire are large, resulting in low efficiency.

On the other hand, the piezoelectric transformer uses a piezoelectric ceramic material such as lead zirconate titanate (PZT) or a piezoelectric crystal material such as lithium niobate on the primary side (input side).
And the secondary side (output side) electrode is attached, an AC voltage near the resonance frequency of the piezoelectric transformer is applied to the primary side electrode to mechanically vibrate the piezoelectric transformer, and this mechanical vibration is converted by the piezoelectric effect. The high voltage power is taken out from the secondary side electrode. Further, it has a feature that it can be made smaller, especially thinner than an electromagnetic transformer, and high conversion efficiency can be achieved.

A conventional piezoelectric transformer will be described below with reference to the drawings. FIG. 10 is a schematic view of a conventional Rosen type piezoelectric transformer 31, which is a rectangular plate made of a piezoelectric ceramic material such as lead zirconate titanate (PZT), a primary side (input side) on the main surface and a secondary side on the end surface. It is configured with an electrode on the side (output side). As indicated by arrows and P in the figure, the primary side electrode portion is polarized in the thickness direction of the rectangular plate, and the secondary side electrode portion is polarized in the length direction of the rectangular plate. When an AC voltage near the resonance frequency of the piezoelectric transformer is applied to the primary electrode, the piezoelectric transformer causes mechanical vibration that expands and contracts in the length direction, and this mechanical vibration becomes a high voltage at the secondary electrode due to the piezoelectric effect. It is converted and taken out as high voltage power from the secondary electrode.

FIG. 11 shows the piezoelectric transformer 31 shown in FIG.
Is a side view of the rectangular plate, the electrode 1 is formed as the primary side (input side) electrode on the main surface of the rectangular plate, the electrode 2 is formed as the common electrode, and the secondary side (output side) is formed on the end face. An electrode 3 is formed as a side electrode. Then, by applying a high voltage to each of the electrodes 1 and 3 using the electrode 2 as a common electrode, as shown by arrows in FIG.
The secondary electrode portion is polarized in the thickness direction of the rectangular plate, and the secondary electrode portion is polarized in the length direction of the rectangular plate. Then, when an alternating voltage is applied to the electrode 1 with the electrode 2 as a common electrode, stretching vibration in the length direction having the displacement distribution shown in the figure occurs, and the electrode 3 can be converted into a high voltage for extraction. Further, this type of piezoelectric transformer has a rectangular plate piezoelectric transformer having a half size, as can be seen from the displacement distribution shown in FIG.
It is also called a λ / 2 Rosen type piezoelectric transformer because it excites a stretching vibration of a wavelength (one wavelength is represented by λ).

Since the power source of the portable device is usually a battery, the power source voltage is low voltage direct current such as 3V, 5V, 9V and 12V. Then, for example, in the liquid crystal backlight of these portable devices, 1000V is generated at the start of lighting of the cold cathode tube.
A high-frequency voltage of about rms and about 500 Vrms in a steady state is required. That is, it is necessary for a piezoelectric transformer for a liquid crystal backlight for portable devices to be able to obtain high voltage alternating current from low voltage alternating current. However, the piezoelectric transformers shown in FIGS. 10 and 11 have a small input electrode area and thus a small input capacitance (large input impedance). Therefore, when a low-voltage AC signal is input, the current flowing into the input electrode is small and the output voltage is low. As a result, a high AC voltage cannot be obtained. Therefore, when a high DC voltage is required, there is a problem that an electromagnetic transformer having a relatively large turns ratio is required to boost the input AC voltage.

FIG. 12 is a schematic view of a piezoelectric transformer 32 developed to solve such a problem. The primary side is formed on a main surface of a rectangular plate made of a piezoelectric ceramic material such as lead zirconate titanate (PZT). A secondary side (output side) electrode is attached to the (input side) and the end face. As indicated by the arrow and symbol P in the figure, the primary electrode portion is polarized in the thickness direction of the rectangular plate, and the secondary electrode portion is polarized in the length direction of the rectangular plate. When an AC voltage near the resonance frequency of the piezoelectric transformer is applied to the primary side electrode, the piezoelectric transformer causes mechanical vibration that expands and contracts in the length direction, and this mechanical vibration causes a high voltage AC voltage at the secondary side electrode due to the piezoelectric effect. It can be extracted as high-voltage power after being converted to.

FIG. 13 shows the piezoelectric transformer 32 shown in FIG.
FIG. 3 is a side view of the rectangular plate, where electrodes 1, 2, and 3 are formed as primary side (input side) electrodes on the main surface of the rectangular plate, and secondary side (output side) electrodes are formed on the end surface. The electrode 4 is formed. Then, by applying a high voltage to each of the electrodes 1 and 2, and the electrode 4 with the electrode 3 as a common electrode, the primary side electrode portion is formed in the thickness direction of the rectangular plate as indicated by arrows in the figure. The secondary electrode part is polarized in the longitudinal direction of the rectangular plate. Then, when an alternating voltage is applied to the electrodes 1 and 2 with the electrode 2 as a common electrode, stretching vibration in the length direction having the displacement distribution shown in FIG.
It can be taken out after being converted into a high voltage from the electrode 4. As can be seen from the displacement distribution shown in FIG. 13, this type of piezoelectric transformer excites a stretching vibration of ⅔ wavelength (one wavelength is represented by λ) in the rectangular plate piezoelectric transformer, so that 3λ / Also called type 2 Rosen piezoelectric transformer. The piezoelectric transformer 32 shown in FIGS.
Since the area of the input electrode is larger than that of the piezoelectric transformers 31 shown in FIGS. 0 and 11, the input capacitance is large (the input impedance is small), and therefore the current flowing into the input electrode is large even when a low-voltage AC signal is input. It is possible,
Higher voltage can be obtained as output. However, it is not possible to obtain a sufficiently high voltage as an output to turn on the backlight, and there is still a problem that an electromagnetic transformer for boosting the input AC voltage is still required.

FIG. 14 is a schematic view of another piezoelectric transformer 33 invented with respect to the problem of low voltage driving, in which 1 is formed on the main surface of a rectangular plate made of a piezoelectric ceramic material such as lead zirconate titanate (PZT). It is configured by attaching electrodes on the secondary side (input side) and the secondary side (output side) (NEC Technical Report).
1994 vol. 47 No. 10 106-11
Page 0). As indicated by the arrow and symbol P in the figure, the primary electrode portion is polarized in the thickness direction of the rectangular plate, and the secondary electrode portion is polarized in the length direction of the rectangular plate. When an AC voltage near the resonance frequency of the piezoelectric transformer is applied to the primary side electrode, the piezoelectric transformer causes mechanical vibration that expands and contracts in the length direction, and this mechanical vibration causes a high voltage AC voltage at the secondary side electrode due to the piezoelectric effect. It can be extracted as high-voltage power after being converted to.

FIG. 15 shows the piezoelectric transformer 33 shown in FIG.
FIG. 3 is a side view of the rectangular plate viewed from the side, and electrodes 1 and 2 and electrodes 3 and 4 are provided as primary side (input side) electrodes on the main surface of the rectangular plate.
Are formed, and electrodes 5 and 6 are formed as secondary side (output side) electrodes on the end face. Then, by applying high voltages of opposite polarities to the electrodes 1 and 3 with the electrodes 2 and 4 as a common electrode, the primary side electrode portion has a rectangular plate thickness as shown by arrows in FIG. The secondary side electrode portion is polarized in the length direction of the rectangular plate by applying a high voltage to the electrodes 5 and 6 with the electrodes 2 and 4 as a common electrode. And the electrodes 2 and 4
When an AC voltage is applied to the electrodes 1 and 3 using as a common electrode, stretching vibration in the length direction having the displacement distribution shown in FIG. As can be seen from the displacement distribution shown in FIG. 15, this type of piezoelectric transformer excites a stretching vibration of three-quarter wavelength (one wavelength is represented by λ) in the rectangular plate piezoelectric transformer. It is also called a / 2 type Rosen piezoelectric transformer. This type of piezoelectric transformer has a rectangular plate piezoelectric transformer, as can be seen from the displacement distribution shown in FIG.
It is also called a 3λ / 2 type Rosen piezoelectric transformer because it excites stretching vibration of three wavelengths (one wavelength is represented by λ). In the piezoelectric transformer 33 shown in FIGS.
Since the area of the input electrode is larger than that of the piezoelectric transformers 31 shown in FIGS. 0 and 11, the input capacitance is large (the input impedance is small), and therefore the current flowing into the input electrode is large even when a low-voltage AC signal is input. It is possible,
Higher voltage can be obtained as output. However, it is not possible to obtain a high voltage as an output to turn on the backlight, and there is still a problem that an electromagnetic transformer for boosting the input AC voltage is required.

[0012]

In the conventional piezoelectric transformer described above, since the input electrode area is small and the input capacitance is small, the input impedance becomes large, and when a low-voltage AC signal is input, it flows into the input electrode. There is a problem that the current is small, and as a result, it is not possible to obtain a sufficiently high voltage as an output to turn on the backlight. Therefore, in the conventional inverter circuit (step-up circuit) using the piezoelectric transformer, the input AC voltage is boosted by the electromagnetic transformer and then input to the piezoelectric transformer.

To solve this problem, 3λ
In a 1/2 type Rosen piezoelectric transformer, the input electrode area is increased to increase the input capacitance, and the current flowing into the input electrode is increased even when a low-voltage AC signal is input to obtain a higher voltage as an output. An inverter circuit (step-up circuit) using a transformer has been proposed, but it is not possible to obtain a high voltage enough to turn on the backlight as an output, and again an electromagnetic transformer for stepping up the input AC voltage is required. There is still a problem. Further, since only the 3λ / 2 mode Rosen type piezoelectric transformer is used as the piezoelectric transformer, there is a problem that the degree of freedom in designing the shape and the driving frequency is small.

In order to solve this problem, the object of the present invention is to provide a Rosen type piezoelectric transformer of any mode,
Inverter circuit using a piezoelectric transformer (boosting voltage) to increase the input electrode area to increase the input capacitance and increase the current flowing into the input electrode even when a low-voltage AC signal is input Circuit).

[0015]

To achieve the above object, the first embodiment of the present invention is directed to a rectangular plate made of a piezoelectric material, in which a primary side (input side) electrode and a secondary side (output side) electrode are provided. The primary side electrode part is polarized in the thickness direction of the rectangular plate, the secondary side electrode part is polarized in the length direction of the rectangular plate, and an AC voltage is applied to the primary side electrode to form a rectangular plate. The primary side electrode of the Rosen type piezoelectric transformer that causes mechanical vibration that expands and contracts in the lengthwise direction of the half wavelength to extract the voltage from the secondary side electrode part is 55% to 90% of the main surface area of the piezoelectric transformer. The second embodiment of the present invention is characterized in that a primary side (input side) electrode and a secondary side (output side) electrode are formed on a rectangular plate made of a piezoelectric material. The electrode part is polarized in the thickness direction of the rectangular plate, the secondary electrode part is polarized in the length direction of the rectangular plate, and it is connected to the primary side electrode. A voltage is applied to the rectangular plate to cause mechanical vibration that expands and contracts in the lengthwise direction of one wavelength, and the voltage is extracted from the secondary-side electrode section. Forming a first electrode on a first region of the second electrode and forming a second electrode on a part of the second region,
A common electrode is formed on the other main surface of the piezoelectric transformer, and
The third embodiment of the present invention is characterized by a piezoelectric transformer for extracting a voltage from the secondary side electrode , and a rectangular plate made of a piezoelectric material is provided with a primary side (input side) electrode and a secondary side (output side) electrode. And the primary side electrode part is polarized in the thickness direction of the rectangular plate,
The secondary electrode part is polarized in the length direction of the rectangular plate, an AC voltage is applied to the primary electrode, and mechanical vibrations are generated in the rectangular plate that expands and contracts in the length direction of ⅔ wavelength. The first electrode is formed in the first region of the three regions corresponding to approximately three equal parts of the main surface of the Rosen type piezoelectric transformer for extracting the voltage from the electrode portion, and the first region is formed in the second region adjacent to the first region. The second electrode is formed, the third electrode is formed in a part of the third region adjacent to the second region, and the first electrode, the second electrode, and the third electrode are connected to the primary side ( The fourth embodiment of the present invention is characterized in that a rectangular plate made of a piezoelectric material is used as an input side) electrode.
Forming a secondary side (input side) electrode and a secondary side (output side) electrode,
The primary side electrode part is polarized in the thickness direction of the rectangular plate, the secondary side electrode part is polarized in the length direction of the rectangular plate, an AC voltage is applied to the primary side electrode, and the rectangular plate is halved. A region that is approximately ⅔ of the principal surface of a Rosen type piezoelectric transformer that causes mechanical vibration that expands and contracts in the lengthwise direction of the wavelength and takes out voltage from the secondary side electrode section.
Forming a first electrode and a third electrode on the first electrode and
Between the third electrodes and approximately 1/3 of the central portion of the main surface
The second feature is a piezoelectric transformer in which a second electrode is formed in a part of the region, and the first electrode, the second electrode, and the third electrode are primary side (input side) electrodes.

[0016]

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

(Embodiment 1) FIG. 1 is a schematic view of a piezoelectric transformer which is an example of Embodiment 1 of the present invention.
FIG. 4 is a side view showing a displacement distribution and a charge distribution of the piezoelectric transformer. 1 and 2, a piezoelectric transformer 1 is a rectangular plate made of a piezoelectric ceramic material such as lead zirconate titanate (PZT), and an electrode 1 is formed as a primary side (input side) electrode on one main surface thereof. The electrode 2 is formed as a common electrode on the opposite surface, and the electrode 3 is formed as a secondary (output side) electrode on the end surface thereof. These electrodes are made of a metal such as silver, nickel or gold, and are formed by a method such as vapor deposition, sputtering, printing or plating. Then, as indicated by an arrow and P in FIG. 1, the primary electrode portion is polarized in the thickness direction of the rectangular plate, and the secondary electrode portion is polarized in the length direction of the rectangular plate. When an AC voltage near the resonance frequency of the piezoelectric transformer 1 is applied to the electrodes 1 and 2, the piezoelectric transformer 1 causes mechanical vibration that expands and contracts in the length direction, and this mechanical vibration is generated by the piezoelectric effect in the secondary electrode portion. It can be extracted as high voltage power after being converted to high voltage.

The polarization of the piezoelectric transformer 1 is 1 as shown by an arrow in FIGS. 1 and 2 by applying a high voltage to each of the electrodes 1 and 3 using the electrode 2 as a common electrode.
The secondary electrode portion is polarized in the thickness direction of the rectangular plate, and the secondary electrode portion is polarized in the length direction of the rectangular plate. When an AC voltage is applied to the electrode 1 using the electrode 2 as a common electrode, a stretching vibration in the length direction having the displacement distribution shown in FIG. 2 is generated, and the electrode 3 can be converted into a high voltage for extraction. As can be seen from the displacement distribution shown in FIG. 2, the piezoelectric transformer 1 according to this embodiment excites a half-wave stretching vibration in a rectangular plate, so that the piezoelectric transformer 1 is a λ / 2 mode Rosen type piezoelectric transformer. be called.

In the λ / 2 mode Rosen type piezoelectric transformer 1 shown in FIG. 1, the charge distribution induced during operation (during vibration) has the same sign throughout the region as shown in FIG. And
A method of forming the input electrodes on more than half of the main surface of the piezoelectric transformer 1 as shown in FIGS. 1 and 2 rather than forming the input electrodes on almost half of the main surface as in the conventional piezoelectric transformer shown in FIGS. However, the input capacitance becomes large (the input impedance becomes small), so that even when a low-voltage AC signal is input, the current flowing into the input electrodes 1 and 2 can be increased, and a high AC voltage can be obtained as an output. it can. For example, it is possible to obtain a high voltage sufficient to turn on a cold cathode tube which is a backlight of a liquid crystal display. For example,
In the experiment, the area of the electrode 1 as the input electrode (and the electrode 2 as the common electrode) is 55 to 90% of the main surface area, particularly 60 to
A remarkable effect was obtained at 85%. Since the conventional piezoelectric transformer has a large input impedance, it is necessary to boost the input voltage with an electromagnetic transformer in order to increase the input current.However, in the piezoelectric transformer of the present invention, the input impedance is small, so that the electromagnetic transformer should be eliminated. You can In addition, since it is possible to vibrate vigorously, there is an effect that the driving efficiency can be improved.

FIG. 3 is a schematic view of a piezoelectric transformer which is another embodiment of the second embodiment of the present invention. In the embodiments of FIGS. 1 and 2, the electrode 3 is formed on the end face as an output electrode. Even if the electrode 4 is formed as an output electrode near the end face on the main surface as shown in FIG. 3, the step-up ratio is slightly reduced, but the input impedance can be reduced, and therefore a low-voltage AC signal is input. Even in this case, the current flowing into the input electrodes 1 and 2 can be increased, and a high voltage sufficient to turn on the backlight can be obtained as an output. It goes without saying that the same effect can be obtained that the electromagnetic transformer for boosting the input AC voltage can be eliminated.

(Second Embodiment) FIG. 4 is a schematic view of a piezoelectric transformer which is an example of the second embodiment of the present invention.
FIG. 5 is a side view showing the displacement distribution and charge distribution of the piezoelectric transformer of FIG. In FIGS. 4 and 5, the piezoelectric transformer 3 is a rectangular plate made of a piezoelectric ceramic material such as lead zirconate titanate (PZT), and the electrode 1 and the electrode 2 as primary side (input side) electrodes are provided on one main surface thereof. Electrode 3 is formed as a common electrode on the opposite surface, and the secondary side (output side) is formed on the end surface.
The electrode 4 is formed as an electrode. These electrodes can be formed of a metal material such as silver, nickel or gold by a method such as vapor deposition, sputtering, printing or plating. And
As shown by arrows and P in FIG. 4, the electrode part 1 and the electrode part 2 which are the primary side electrodes are polarized in opposite directions in the thickness direction of the rectangular plate, and the secondary side electrode part is of the rectangular plate. It is polarized in the length direction. When an AC voltage near the resonance frequency of the piezoelectric transformer 3 is applied to the electrodes 1 and 2 with the electrode 3 as a common electrode, the piezoelectric transformer 3 causes mechanical vibration that expands and contracts in the longitudinal direction, and this mechanical vibration is generated by the piezoelectric effect. It can be taken out as high-voltage power after being converted into a high-voltage AC voltage at the secondary electrode part.

The polarization of the piezoelectric transformer 3 is indicated by an arrow in FIGS. 4 and 5 by applying a high voltage in the opposite direction to the electrodes 1 and 2 and a high voltage to the electrode 4 with the electrode 3 as a common electrode. In addition, the primary electrode portions are polarized in the thickness direction of the rectangular plate, and the secondary electrode portions are polarized in the length direction of the rectangular plate. When an AC voltage near the resonance frequency of the piezoelectric transformer 3 is applied to the electrodes 1 and 2 with the electrode 3 as a common electrode, stretching vibration in the length direction having the displacement distribution shown in FIG. It can be converted into voltage and taken out. Further, as can be seen from the displacement distribution shown in FIG. 5, the piezoelectric transformer 3 of this embodiment is a λ mode Rosen type piezoelectric transformer because it excites stretching vibration of one wavelength in the rectangular plate.

In the λ-mode Rosen type piezoelectric transformer 3 shown in FIGS. 4 and 5, the charge distribution induced by vibration during operation (at the time of vibration) is coded at a substantially central position of the piezoelectric transformer 3 as shown in FIG. Is reversed, the input electrode is
As compared with the conventional piezoelectric transformer shown in FIG. 13, the electrodes are formed on almost half of the main surface where the polarities of the induced charges of the piezoelectric transformer 3 are the same as shown in FIGS. 1 is formed, and the electrode 2 is formed on a part of another half of the main surface where the polarities of the induced charges are opposite.
When the AC voltage is applied by short-circuiting the electrode 2 and the electrode 2, the input capacitance becomes larger (the input impedance becomes smaller). Therefore, even when an AC signal of a low voltage is input, the input electrode 1,
The current flowing into 2 can be increased, and an AC voltage high enough to turn on the backlight can be obtained as an output. For example, in an experiment, a remarkable effect could be confirmed when the area of the electrode 2 was set to about 10 to 40% of the main surface area of the piezoelectric transformer 3. Since the conventional piezoelectric transformer has a large input impedance, it is necessary to boost the input voltage with an electromagnetic transformer in order to increase the input current.However, the piezoelectric transformer of the present invention has a low input impedance and therefore the input AC voltage is boosted. It is possible to eliminate the electromagnetic transformer for doing so. In addition, since the λ-mode vibration is easily excited, the driving efficiency can be improved.

Although the electrode 4 is formed as an output electrode on the end face in the above-mentioned embodiment, even if the electrode 4 is formed near the end face on the main surface, the step-up ratio is slightly lowered,
The input impedance can be reduced, so that the current flowing into the input electrodes 1 and 2 can be increased even when a low-voltage AC signal is input, and for example, a sufficiently high voltage for lighting a backlight can be obtained as an output. it can. It goes without saying that the same effect can be obtained that the electromagnetic transformer for boosting the input AC voltage can be eliminated.

Further, as shown in FIGS. 4 and 5, the electrode 1 is formed in almost half of the main surface of the piezoelectric transformer 3 having the same polarity of the induced charges, and the main surface having the opposite polarity of the induced charges is formed. Even if the electrodes 2 are formed in a part of the half and the electrodes 1 and 2 are polarized in the same direction and AC voltages of opposite signs are applied to the electrodes 1 and 2 during driving, the input capacitance is large ( The input impedance becomes small). Therefore, the current flowing into the input electrodes 1 and 2 can be increased even when a low-voltage AC signal is input, and a sufficiently high voltage for lighting the backlight can be obtained as an output. You can It goes without saying that the same effect can be obtained that the electromagnetic transformer for boosting the input AC voltage can be eliminated.

(Embodiment 3) FIG. 6 is a schematic view of a piezoelectric transformer which is an example of Embodiment 3 of the present invention.
FIG. 7 is a side view showing the displacement distribution and charge distribution of the piezoelectric transformer shown in FIG. In FIGS. 6 and 7, the piezoelectric transformer 4 is a rectangular plate made of a piezoelectric ceramic material such as lead zirconate titanate (PZT), and one main surface thereof has electrodes 1 and 2 as primary side (input side) electrodes. Electrode 3 is formed on the opposite surface, and electrode 4 is formed corresponding to these electrodes, and 2 is formed on the end surface.
The electrode 5 is formed as the next side (output side) electrode. For these electrodes, metals such as silver and nickel are deposited, sputtered,
It can be formed by a method such as printing or plating. Then, as indicated by arrows and P in FIG. 6, adjacent portions of the electrode portion 1, the electrode portion 2, and the electrode portion 3 which are the primary side electrodes are polarized in opposite directions in the thickness direction of the rectangular plate. The secondary electrode part is polarized in the length direction of the rectangular plate. When an AC voltage near the resonance frequency of the piezoelectric transformer 4 is applied to the electrodes 1, 2 and 3 with the electrode 4 as a common electrode, the piezoelectric transformer 4 causes mechanical vibration that expands and contracts in the length direction, and this mechanical vibration is generated. Due to the piezoelectric effect, it can be extracted as high-voltage power after being converted into a high-voltage AC voltage at the secondary electrode part.

The polarization of the piezoelectric transformer 4 is obtained by applying a high voltage DC voltage in the opposite direction to the portions adjacent to the electrodes 1, 2 and 3 with the electrode 4 as a common electrode and a high voltage DC voltage to the electrode 5. As shown by the arrows in FIGS. 6 and 7, the primary electrode portion is polarized in the thickness direction of the rectangular plate, and the secondary electrode portion is polarized in the length direction of the rectangular plate. Then, when an alternating voltage near the resonance frequency of the piezoelectric transformer 4 is applied to the electrodes 1, 2 and 3 with the electrode 4 as a common electrode, the piezoelectric transformer 4 has stretching vibration in the longitudinal direction having the displacement distribution shown in FIG. Is excited, converted into a high-voltage AC voltage by the piezoelectric effect, and can be taken out from the electrode 5. As can be seen from the displacement distribution shown in FIG. 7, the piezoelectric transformer 4 of this embodiment excites the stretching vibration of ⅔ wavelength in the rectangular plate, so that it is a Rosen type piezoelectric transformer of 3λ / 2 mode. is there.

In the 3λ / 2 mode piezoelectric transformer 4 shown in FIGS. 6 and 7, the charge distribution induced by vibration during operation (at the time of vibration) is almost the same in the longitudinal direction of the piezoelectric transformer 4 as shown in FIG. Since the sign is inverted at the position of ⅓, the input electrodes are formed on the region of about ⅔ of the main surface as in the conventional piezoelectric transformer shown in FIGS.
As shown in, the electrode 1 is formed in a region that is approximately 1/3 of the principal surface of the piezoelectric transformer 3 having the same polarity of the induced charges, and the electrode 1 is formed at a region of approximately 1/3 of the principal surface of the opposite polarity of the induced charges An electrode 2 is formed in a region, and an electrode 3 is formed in a part of a region that is approximately ⅓ of the main surface having the same polarity of induced charges. When driving, the electrodes 1 and 2 and 3 are short-circuited When a voltage is applied, the input capacitance becomes larger (the input impedance becomes smaller), so that the current flowing into the input electrodes 1, 2, and 3 can be increased even when a low-voltage AC signal is input, For example, a high voltage enough to turn on the backlight can be obtained as an output. According to the result of an actual experiment, the electrode 3 is set to be 5 to 2 of the main surface area of the piezoelectric transformer 4.
When set to 0%, a remarkable effect could be confirmed.
Since the input capacitance is large and the input impedance is small, the electromagnetic transformer for boosting the input AC voltage can be eliminated. Further, since the vibration of the 3λ / 2 mode can be strongly excited, there is also an effect that the driving efficiency can be improved.

In the above embodiment, the electrode 5 is formed on the end face as the output electrode. However, if the electrode 5 is formed near the end face on the main surface, the step-up ratio is slightly lowered, but
The input impedance can be reduced, so that the current flowing into the input electrodes (electrode 1, electrode 2, and electrode 3) can be increased even when a low-voltage AC signal is input, and it is sufficient to turn on the backlight as an output, for example. It is possible to obtain a high voltage. It goes without saying that the same effect can be obtained that the electromagnetic transformer for boosting the input AC voltage can be eliminated.

Further, as shown in FIGS. 6 and 7, the electrode 1 is formed in the first region, which is approximately 1/3 of the main surface of the piezoelectric transformer 4, and the induced charge has approximately 1 of the main surface having the opposite polarity. The electrode 2 is formed in the second region of / 3, and the electrode 3 is formed in a part of the third region which is approximately ⅓ of the main surface having the same polarity of the induced charges. Even if the electrodes 2 and 3 are polarized to the same polarity and an alternating voltage with the opposite sign is applied to the electrodes 1 and 2 and an alternating voltage with the same sign is applied to the electrodes 3 during driving, Since the capacity is large (the input impedance is small), the current flowing into the input electrode can be increased even when a low-voltage AC signal is input, and for example, a sufficiently high voltage to output the backlight is obtained as an output. be able to. It goes without saying that the same effect can be obtained that the electromagnetic transformer for boosting the input AC voltage can be eliminated.

(Fourth Embodiment) FIG. 8 is a schematic view of a piezoelectric transformer according to an embodiment of the fourth embodiment of the present invention.
FIG. 9 is a side view showing a displacement distribution and a charge distribution of the piezoelectric transformer shown in FIG. In FIGS. 8 and 9, the piezoelectric transformer 5 is a rectangular plate made of a piezoelectric ceramic material such as lead zirconate titanate (PZT), and its one main surface has electrodes 1 and 3 as primary side (input side) electrodes. An electrode 5, an electrode 2, an electrode 4, and an electrode 6 are formed on the opposite surface as a common electrode, and an electrode 7 and an electrode 8 are formed as secondary side (output side) electrodes. These electrodes are vapor-deposited with metals such as silver, nickel and gold.
It can be formed by a method such as sputtering, printing, or plating. Then, as indicated by arrows and P in FIG. 8, the electrode portion 1 and the electrode portion 5, which are the primary side electrodes, are polarized in opposite directions in the thickness direction, and the electrode portion 1 and the electrode portion 3 are respectively polarized. It is polarized in the same direction in the thickness direction. The secondary output part is polarized in the opposite direction in the length direction of the rectangular plate as shown in FIG. Electrode 1 with electrodes 2, 4 and 6 as common electrodes
When an AC voltage near the resonance frequency of the piezoelectric transformer 5 is applied to the electrodes 3 and 5, the piezoelectric transformer 5 causes mechanical vibration that expands and contracts in the length direction, and this mechanical vibration causes the secondary side electrode portion due to the piezoelectric effect. After being converted into a high-voltage AC voltage with, the high-voltage voltage can be taken out from the electrode 7.

The polarization of the piezoelectric transformer 5 depends on the electrodes 2 and 4.
And electrode 6 as a common electrode, a high voltage DC voltage in the same direction is applied to electrodes 1 and 3, a high voltage DC voltage in the opposite direction is applied to electrode 5, and a high voltage DC voltage is applied to electrode 7 (or electrode 8 or electrode 7 and electrode 8). By applying a voltage, as shown by the arrows in FIGS. 8 and 9, the primary electrode portions are polarized in the thickness direction of the rectangular plate, and the secondary electrode portions are polarized in the length direction of the rectangular plate. Then, when an AC voltage in the vicinity of the resonance frequency of the piezoelectric transformer 5 is applied to the electrodes 1, 3 and 5 with the electrodes 2, 4 and 6 as a common electrode, the piezoelectric transformer 5 expands and contracts in the longitudinal direction. As shown in the displacement distribution shown in FIG. 9, the piezoelectric transformer 5 of this embodiment excites the stretching vibration of ⅔ wavelength to the rectangular plate, so that the 3λ / 2 mode is generated. It is a Rosen type piezoelectric transformer.

In the 3λ / 2 mode Rosen type piezoelectric transformer 5 shown in FIGS. 8 and 9, the charge distribution induced by vibration during operation (at the time of vibration) is as shown in FIG.
The sign is inverted at positions of approximately ⅓ and ⅔ in the length direction of the. Rather than forming the input electrode in a region of approximately ⅔ of the main surface as in the conventional piezoelectric transformer shown in FIGS.
As shown in FIGS. 6 and 7, the electrode 1 is formed in a region which is approximately ⅔ of the principal surface of the piezoelectric transformer 3 having the same polarity of the induced charges.
And the electrode 3 are formed, and the electrode 5 is formed in a part of a region that is approximately 1/3 of the center of the main surface having the opposite polarity of the induced charge, and the electrodes 1, 3 and 5 are short-circuited during driving. The input capacitance is larger (the input impedance is smaller) when the AC voltage is applied, and therefore the current flowing into the input electrode 1, the input electrode 2 and the input electrode 3 should be increased even when the low voltage AC signal is input. It is possible to obtain, for example, an AC voltage high enough to turn on the backlight as an output. That is, the electromagnetic transformer for boosting the input AC voltage in the booster circuit can be eliminated. Also, 3
Since the λ / 2 mode vibration is easily excited, there is also an effect that the driving efficiency can be improved.

Although the electrode 7 is used as the output electrode in the above embodiment, the electrode 8 may be used as the output electrode or the electrodes 7 and 8 may be used as the output electrodes.
It goes without saying that the same effect can be obtained.

Further, as shown in FIGS. 8 and 9, the electrode 1 is formed in a region which is approximately 1/3 of the main surface of the piezoelectric transformer 4, which has the same polarity of the induced charges, and has the opposite polarity of the induced charges. The electrode 5 is formed in a region of approximately ⅓ of the surface, and the electrode 3 is formed in a part of a region of the main surface that has the same polarity of the induced charges and is approximately ⅓. 3 and the electrode part 5 are polarized to the same polarity, and even if an AC voltage of the same sign is applied to the electrodes 1 and 3 and an AC voltage of the opposite sign is applied to the electrode 5 during driving, the input capacitance is large (input impedance Therefore, the current flowing into the input electrode can be increased even when a low-voltage AC signal is input,
As an output, it is possible to obtain a sufficiently high voltage to turn on the backlight. It goes without saying that the same effect can be obtained that the electromagnetic transformer for boosting the input AC voltage can be eliminated.

[0036]

According to the first aspect of the present invention, in the λ / 2 mode Rosen type piezoelectric transformer, the input electrode area is increased and the input capacitance is increased (input impedance is reduced). Even when a low voltage AC signal is input, the current flowing into the input electrode can be increased and a high voltage can be obtained as an output.
Then, in the AC voltage booster circuit using the piezoelectric transformer of the present invention, it is possible to provide a piezoelectric transformer having an effect of eliminating the electromagnetic transformer for boosting the input AC voltage.

According to the second aspect of the present invention, in the λ mode Rosen type piezoelectric transformer, the input electrode area is increased and the input capacitance is increased (input impedance is reduced). Even when an AC signal is input, the current flowing into the input electrode can be increased and a high voltage can be obtained as an output. Then, in the AC voltage booster circuit using the piezoelectric transformer of the present invention, it is possible to provide a piezoelectric transformer having an effect of eliminating the electromagnetic transformer for boosting the input AC voltage.

According to the third aspect of the present invention, in the 3λ / 2 mode Rosen type piezoelectric transformer, by increasing the input electrode area and increasing the input capacitance (the input impedance is small), a low voltage is applied. Even when the AC signal is input, the current flowing into the input electrode can be increased and a high voltage can be obtained as the output.
Then, in the AC voltage booster circuit using the piezoelectric transformer of the present invention, it is possible to provide a piezoelectric transformer having an effect of eliminating the electromagnetic transformer for boosting the input AC voltage.

According to the fourth aspect of the present invention, in the 3λ / 2 mode Rosen type piezoelectric transformer, the input electrode area is increased and the input capacitance is increased (the input impedance is reduced). Even when the AC signal is input, the current flowing into the input electrode can be increased and a high voltage can be obtained as the output.
Then, in the AC voltage booster circuit using the piezoelectric transformer of the present invention, it is possible to provide a piezoelectric transformer having an effect of eliminating the electromagnetic transformer for boosting the input AC voltage.

[Brief description of drawings]

FIG. 1 is a schematic view of a λ / 2 mode Rosen type piezoelectric transformer of the present invention.

FIG. 2 is a side view, a displacement distribution, and a charge distribution diagram of a λ / 2 mode Rosen type piezoelectric transformer of the present invention.

FIG. 3 is a schematic view of a λ / 2 mode Rosen type piezoelectric transformer according to another embodiment of the present invention.

FIG. 4 is a schematic view of a λ mode Rosen type piezoelectric transformer of the present invention.

FIG. 5 is a side view, a displacement distribution, and a charge distribution diagram of a λ-mode Rosen type piezoelectric transformer of the present invention.

FIG. 6 is a schematic view of a 3λ / 2 mode Rosen type piezoelectric transformer of the present invention.

FIG. 7 is a side view, displacement distribution, and charge distribution diagram of the 3λ / 2 mode Rosen type piezoelectric transformer of the present invention.

FIG. 8 is a schematic view of a 3λ / 2 mode Rosen type piezoelectric transformer of the present invention.

FIG. 9 is a side view, displacement distribution, and charge distribution diagram of the 3λ / 2 mode Rosen type piezoelectric transformer of the present invention.

FIG. 10 is a schematic view of a conventional λ / 2 mode Rosen type piezoelectric transformer.

FIG. 11 is a side view, a displacement distribution and a charge distribution diagram of a conventional λ / 2 mode Rosen type piezoelectric transformer.

FIG. 12 is a schematic view of a conventional λ mode Rosen type piezoelectric transformer.

FIG. 13 is a side view, a displacement distribution, and a charge distribution diagram of a conventional λ mode Rosen type piezoelectric transformer.

FIG. 14 is a schematic view of a conventional 3λ / 2 mode Rosen type piezoelectric transformer.

FIG. 15 is a side view, displacement distribution, and charge distribution diagram of a conventional 3λ / 2 mode Rosen-type piezoelectric transformer.

[Explanation of symbols]

1-5 Piezoelectric transformer 31-33 Piezoelectric transformer

Claims (8)

(57) [Claims] 1. A primary side (input side) electrode and a secondary side (output side) electrode are formed on a rectangular plate made of a piezoelectric material, and the primary side electrode portion is polarized in the thickness direction of the rectangular plate. The secondary electrode part is polarized in the length direction of the rectangular plate, an AC voltage is applied to the primary electrode, and the rectangular plate is expanded and contracted in the length direction of a half wavelength mechanical vibration. And a voltage of the secondary side electrode is taken out from the secondary side electrode. The size of the primary side electrode is 55% to 90% of the main surface area of the piezoelectric transformer. Piezoelectric transformer. 2. A primary side (input side) electrode and a secondary side (output side) electrode are formed on a rectangular plate made of a piezoelectric material, and the primary side electrode portion is polarized in the thickness direction of the rectangular plate. , The secondary side electrode portion is polarized in the lengthwise direction of the rectangular plate, and an AC voltage is applied to the primary side electrode to cause mechanical vibration that expands and contracts in the lengthwise direction of one wavelength in the rectangular plate, In a Rosen type piezoelectric transformer for extracting a voltage from the secondary side electrode portion, the primary side electrode is provided in a first region of two regions corresponding to approximately two equal parts of the main surface of the piezoelectric transformer. It was the first
Electrode , a second electrode provided in a part of the second region, and a common electrode provided on the other main surface of the piezoelectric transformer.
A piezoelectric transformer having a pole and extracting a voltage from the secondary electrode . 3. The alternating voltage is applied by reversing the polarization directions of the first electrode and the second electrode and short-circuiting the first electrode and the second electrode. Piezoelectric transformer described. 4. The polarization directions of the first electrode and the second electrode are made the same, and an alternating voltage of opposite polarity is applied to the first electrode and the second electrode. Piezoelectric transformer described. 5. A rectangular plate made of a piezoelectric material is provided with a primary side (input side) electrode and a secondary side (output side) electrode, and the primary side electrode portion is polarized in the thickness direction of the rectangular plate. The secondary side electrode part is polarized in the lengthwise direction of the rectangular plate, an AC voltage is applied to the primary side electrode, and the rectangular plate is mechanically expanded and contracted in the lengthwise direction of ⅔ wavelength. And a first electrode is formed in a first region of three regions corresponding to approximately three equal parts of the main surface of the piezoelectric transformer. A second electrode is formed in a second region adjacent to the first region, and the second electrode is formed.
Forming a third electrode in a part of the third region adjacent to the region of 1), and using the first electrode, the second electrode, and the third electrode as primary side (input side) electrodes. Piezoelectric transformer characterized by. 6. The first electrode and the third electrode have the same polarization direction, the first electrode and the second electrode have opposite polarization directions, and the first electrode and the second electrode have the same polarization direction. The piezoelectric transformer according to claim 5, wherein the third electrode is short-circuited to apply an AC voltage. 7. The first electrode, the second electrode, and the third electrode are made to have the same polarization direction, and an alternating voltage of opposite polarity is applied to the first electrode and the second electrode, and the first electrode is applied. Electrode and the third
The piezoelectric transformer according to claim 5, wherein an alternating voltage having a reverse polarity is applied to the electrode of. 8. A primary side (input side) electrode and a secondary side (output side) electrode are formed on a rectangular plate made of a piezoelectric material, and the primary side electrode portion is polarized in the thickness direction of the rectangular plate. The secondary side electrode part is polarized in the lengthwise direction of the rectangular plate, an AC voltage is applied to the primary side electrode, and the rectangular plate is mechanically expanded and contracted in the lengthwise direction of ⅔ wavelength. In a region of the Rosen type piezoelectric transformer that extracts a voltage from the secondary side electrode portion and is approximately ⅔ of the main surface of the piezoelectric transformer.
Forming an electrode and a third electrode , the first electrode and the front electrode
Note Between the third electrodes and approximately 1/3 of the center of the main surface
There the second electrode formed on a part of the region, before Symbol first electrode and the second electrode and the third electrode primary side (input side)
A piezoelectric transformer characterized by being an electrode.