JP2000040844A - Piezoelectric transformer and driving method thereof - Google Patents

Abstract

An object of the present invention is to provide a thin and low-profile multilayer piezoelectric transformer while ensuring an insulation distance between input and output, and to provide a method of driving the multilayer piezoelectric transformer. An input unit includes input internal electrodes.
5b, and the electrodes are polarized in opposite directions in the thickness direction. The output unit 13 includes output internal electrodes 16a and 16b.
And the electrodes are polarized in the direction opposite to the thickness direction. The input unit 12 and the output unit 13 are made of a piezoelectric ceramic octagonal plate 1
1 are divided into two parts in the thickness direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer using radial vibration for input and output in a piezoelectric ceramic regular polygon plate, and a method of driving the piezoelectric transformer.

[0002]

2. Description of the Related Art With the spread of various portable electronic devices such as portable televisions and notebook personal computers, AC adapters that use a commercial AC voltage as a power source and output a DC voltage have been used to supply a DC voltage to these devices. I have. Among the electronic components used for the AC adapter, an electromagnetic transformer has a large volume and affects the conversion efficiency of the AC adapter. In recent years, demands for higher efficiency, smaller size, lower electromagnetic noise and lower power consumption of AC adapters have been increasing, and instead of electromagnetic transformers, piezoelectric transformers using energy of mechanical vibration as a conversion medium have been studied. I have. For the efficiency of the piezoelectric transformer, impedance matching between the output impedance of the piezoelectric transformer and the load is important, but the input impedance of various portable electronic devices connected to the output of the AC adapter is about several Ω to several tens Ω. It is. The output impedance of the piezoelectric transformer is obtained from the respective frequencies ω (= 2πf) and the output side braking capacitance C _{d2 as} in the following equation (1).

[0003]

(Equation 1)

Here, as an example, R = 60Ω, f = 120
At KHz, C _d2 = 22 nF. A of practical dimensions
In order to secure such a large braking capacity in the piezoelectric transformer for the C adapter, a laminated structure using opposing internal electrodes is required.

[0005] As an example of a structure employing an opposing internal electrode on the output side, a structure in which the lamination direction of the internal electrode and the ceramics is the thickness direction using the radial vibration of a piezoelectric ceramic disk can be considered. The radial expansion primary vibration mode is
Among various vibration modes, there is an advantage that the electromechanical coupling coefficient is the highest and the frequency constant is the highest. Here, the output power P _OUT of the piezoelectric transformer is obtained by an equation as shown in the following Expression 2.

[0006]

(Equation 2)

Where k _eff is the effective electromechanical coupling coefficient,
V is the vibration speed, f is the drive frequency, and m is the mass of the transformer. From the above equation 2, when the radially expanded primary vibration mode kr is used, the effective electromechanical coupling coefficient k _eff
In addition, since the driving frequency f increases, the same output power can be realized in a smaller volume as compared with other vibration modes. Furthermore, since the shape is a disk shape, it is low in height, and it is possible to more efficiently dissipate the heat generated by the loss.

[0008]

However, the disadvantages of using the radially expanded primary vibration mode are as follows.
First, when a disk is divided in the thickness direction to provide an input / output unit, the coupling capacitance between the input and output is increased because the distance between the input and output is extremely short, and the resistance to conduction noise is reduced. That is. The second disadvantage is that the edge distance between the input and output is extremely small (power supply for AC adapter is usually 2-3 mm,
Even with reinforced insulation, about 0.5 mm is required). As a third disadvantage, the disk-shaped structure is complicated to manufacture and requires many steps.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thin and low-profile multilayer piezoelectric transformer with a sufficient insulation distance between input and output, and to provide a method of driving the multilayer piezoelectric transformer.

[0010]

According to the present invention, there is provided an input portion having a plurality of electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked on a piezoelectric ceramic regular polygon plate so as to face each other in the thickness direction; Similarly, an output section having a plurality of electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked so as to face each other in the thickness direction is provided, and the piezoelectric ceramic regular polygon is provided between the electrodes in the input section and the output section. A piezoelectric transformer characterized by being polarized in the thickness direction of the plate is obtained.

According to the present invention, there is provided an input section having a plurality of electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked so as to oppose each other in the thickness direction in a central region of a piezoelectric ceramic regular polygon plate. An insulating annular region having no electrodes on the outside, and further including an output unit having a plurality of annular electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked so as to face each other in the thickness direction, the input unit and the A piezoelectric transformer is obtained, characterized in that the space between the electrodes in the output section is polarized in the thickness direction of the piezoelectric ceramic regular polygon plate.

Further, according to the present invention, there is provided an output section having a plurality of electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked so as to face each other in a thickness direction in a central region of a piezoelectric ceramic regular polygon plate, and An insulating annular region having no electrodes on the outside, and further including an input unit having a plurality of annular electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked so as to face each other in the thickness direction, and the input unit and the In the output section, a piezoelectric transformer is obtained in which the electrodes are polarized in the thickness direction of the piezoelectric ceramic regular polygon plate between the electrodes.

According to the present invention, there is provided a method for driving a piezoelectric transformer, characterized in that the piezoelectric transformer is driven in a radially expanding primary vibration mode or a radially expanding tertiary vibration mode of the piezoelectric ceramic regular polygon plate. can get.

[0014]

The piezoelectric transformer of the present invention makes it possible to provide a thin and low-profile laminated piezoelectric transformer with a sufficient insulation distance between input and output.

Further, it is possible to provide a piezoelectric transformer having the same characteristics as described above in the form of a regular polygonal plate which is easy to manufacture.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to FIG. The size of the piezoelectric transformer according to the present embodiment is a regular octagon with one piece being 7.7 mm,
The thickness is 2.3 mm. FIG. 1A is a plan view of the piezoelectric transformer according to the present embodiment (dotted lines are internal electrode patterns), and FIG. 1B is a cross-section showing the internal structure of the piezoelectric transformer of FIG. FIG. 1 (c) shows FIG. 1 (b)
1 (d) is a stress and displacement distribution diagram of the piezoelectric transformer of FIG. 1 (a). As shown in FIG. 1B, the internal electrode pattern is divided into a part functioning as an input part 12 and a part functioning as an output part 13, and each is divided into two in the thickness direction of a piezoelectric transformer regular octagonal plate 11 and provided. ing.

In the central region of the boundary between the input portion 12 and the output portion 13, there is disposed an insulating region 14 of a regular octagonal ceramic having a thickness of 0.3 mm and having no electrode. FIG. 1 (b)
As shown in FIG. 2, the input section 12 has input internal electrodes 15a,
15b, piezoelectric ceramic layers and input internal electrodes are alternately stacked in the central region of the piezoelectric ceramic regular octagonal plate 11 so as to face each other in the thickness direction.
It is polarized in the thickness direction as shown by the arrow in (c). The input unit has a one-layer laminated structure. Output internal electrodes 16a and 16b are also arranged in the output section, and are polarized in opposite directions in the thickness direction, with the other in the thickness direction.
The output unit has a four-layer laminated structure. Polarization was performed in silicon oil at 150 ° C. at an electric field strength of lkv / n] m for both input and output. Table 1 shows the results obtained by connecting a load resistance of 60Ω to the output side of the prototyped piezoelectric transformer and measuring the oscillator constant and the power characteristics.

[0018]

[Table 1]

In the above Table 1, the upper row shows the oscillator constants at the time of micro-vibration, and the lower row shows the oscillator constants and power characteristics in a state where a load is connected. Where fr is the resonance frequency,
C _d2 indicates an output side braking capacity, Qm ₂ indicates an output side mechanical quality factor (reciprocal of a loss coefficient), γ1 indicates an input side capacity ratio, and γ2 indicates an output side capacity ratio.

Next, a second embodiment of the present invention will be described with reference to FIG. The size of the piezoelectric transformer according to the present embodiment is a regular octagon having a side of 7.7 mm and a thickness of 2.3.
mm. FIG. 2A is a plan view of the piezoelectric transformer according to the present embodiment (dotted lines are internal electrode patterns), and FIG. 2B is a cross section showing the internal structure of the piezoelectric transformer of FIG. FIG. 2 (c) is a partially enlarged view of FIG. 2 (b), and FIG. 2 (d) is a stress and displacement distribution diagram in the primary vibration mode of the piezoelectric transformer of FIG. 2 (a). FIG.
FIG. 2E is a stress and displacement distribution diagram in the third vibration mode of the piezoelectric transformer of FIG.

As shown by the dotted internal electrode pattern in FIG. 2A, the internal electrode pattern extends through the insulating region 24 in the outer peripheral direction of the piezoelectric transformer regular octagonal plate 21.
It is provided separately. The central internal electrode pattern functions as the input unit 22, and the internal electrode pattern in the peripheral area functions as the output unit 23. In a boundary region between the input unit 22 and the output unit 23, a ceramic insulating region 24 having no electrodes is arranged.

As shown in FIG. 2 (b), input internal electrodes 25a and 25b are arranged in the input section 22, and the piezoelectric ceramic layer and the input internal electrodes are arranged in the thickness direction in the central region of the piezoelectric ceramic regular octagonal plate 21. Are alternately stacked so as to face each other. As shown by arrows in FIG. 2C, the electrodes are polarized in the opposite direction with respect to one layer in the thickness direction.

The output portion 23 is provided with edge-shaped or annular output internal electrodes 26a and 26b. The piezoelectric ceramic layer and the output internal electrode are opposed to each other in the thickness direction in the outer peripheral region of the piezoelectric ceramic regular octagonal plate 21. Are alternately stacked. As shown by arrows in FIG. 2C, the electrodes are polarized in the opposite direction with respect to one layer in the thickness direction. The polarization between the electrodes is performed at a field strength of 1 kv / mm in silicon oil at 150 ° C. for both input and output.

Table 1 shows the results obtained by connecting a load resistance of 60 Ω to the output side of the prototyped piezoelectric transformer and measuring the vibrator constant and the power characteristics in the radially expanded primary vibration mode.

Next, a third embodiment of the present invention will be described with reference to FIG. The dimensions of the piezoelectric transformer according to the present embodiment are each a square of 20 mm and a thickness of 2.3 m.
m. FIG. 3A is a plan view of the piezoelectric transformer according to the present embodiment (dotted lines are internal electrode patterns).
3B is a cross-sectional view showing the internal structure of the piezoelectric transformer of FIG. 3A, FIG. 3C is a partially enlarged view of FIG. 3B, and FIG. FIG. 3A is a stress and displacement distribution diagram of the piezoelectric transformer. As shown in FIG.
The internal electrode patterns are divided into those that function as the input unit 32 and those that function as the output unit 33, and are provided in two in the thickness direction of the piezoelectric transformer square plate 31, respectively.

In the center area of the boundary between the input section 32 and the output section 33, a 0.3 mm thick ceramic insulating region 34 having no electrode is arranged. As shown in FIG. 3B, the input section 32 has input internal electrodes 35a and 35a.
5b are arranged, and the piezoelectric ceramic layers and the input internal electrodes are alternately laminated so as to face each other in the thickness direction in the central region of the piezoelectric ceramic square plate 31, and FIG.
Polarized in the thickness direction as shown by the arrow in the middle. The input unit has a one-layer laminated structure. Output internal electrodes 36a and 36b are also arranged in the output section, and are polarized in opposite directions in the thickness direction, with the other in the thickness direction. The output unit has a four-layer laminated structure. The polarization is 15 for both input and output.
The test was performed in silicon oil at 0 ° C. with an electric field strength of lkv / n] m. A load resistor 60 is connected to the output side of the prototype piezoelectric transformer.
Table 1 shows the results of measuring the oscillator constant and the power characteristics by connecting Ω.

Next, a fourth embodiment of the present invention will be described with reference to FIG. The dimension of the piezoelectric transformer according to the present embodiment is a square having a side of 20 mm and a thickness of 2.3 mm.
It is. FIG. 4A is a plan view of the piezoelectric transformer according to the present embodiment (dotted lines are internal electrode patterns), and FIG. 4B is a cross section showing the internal structure of the piezoelectric transformer of FIG. 4C is a partially enlarged view of FIG. 4B, and FIG. 4D is a stress and displacement distribution diagram in the primary vibration mode of the piezoelectric transformer of FIG. 4A. As shown in the internal electrode pattern indicated by the dotted line in FIG. 4A, the internal electrode pattern is divided into two in the outer peripheral direction of the piezoelectric transformer square plate 41 via the insulating region 44. The central internal electrode pattern functions as the input section 42, and the internal electrode pattern in the peripheral area functions as the output section 43. In a boundary region between the input unit 42 and the output unit 43, a ceramic insulating region 44 having no electrode is disposed.

As shown in FIG. 4B, input internal electrodes 45a and 45b are arranged in the input section 42. The piezoelectric ceramic layer and the input internal electrodes are arranged in the thickness direction in the central region of the piezoelectric ceramic square plate 41. They are alternately stacked so as to face each other. As shown by the arrows in FIG. 4C, the electrodes are polarized in the thickness direction in opposite directions.

The output portion 43 is provided with edge-shaped or annular output internal electrodes 46a and 46b. The piezoelectric ceramic layer and the output internal electrode face each other in the thickness direction in the outer peripheral region of the piezoelectric ceramic square plate 41. They are alternately stacked. As shown by the arrows in FIG. 4C, the electrodes are polarized in the thickness direction in opposite directions. The polarization between the electrodes is performed at a field strength of 1 kv / mm in silicon oil at 150 ° C. for both input and output.

Table 1 shows the results obtained by connecting a load resistance of 60Ω to the output side of the prototyped piezoelectric transformer and measuring the oscillator characteristics and the power characteristics in the radially expanded primary vibration mode.
Here, from a structural point of view, this embodiment is the same as the above-described second embodiment except that the outer shape of the piezoelectric transformer is different.

In the piezoelectric transformers according to the first to fourth embodiments, the input side, the output side, or both the input and output sides of the piezoelectric ceramic disk and the piezoelectric ceramic square plate have the radially expanding primary vibration mode, respectively. The same effect can be obtained by driving in the third vibration mode. FIG. 2E shows a stress and displacement distribution diagram in the radially expanded tertiary vibration mode in the piezoelectric transformer according to the second embodiment.

In the above-described second and fourth embodiments, the input portions 22 and 42 are provided in the central regions of the piezoelectric ceramic regular octagonal plate 21 and the piezoelectric ceramic square plate 41, respectively, and the output portions 23 and 43 are provided. Are provided in the outer peripheral region of the piezoelectric ceramic regular octagonal plate 21 and the piezoelectric ceramic square plate 41, respectively. If an appropriate number of layers and area can be obtained, the input unit is provided in the outer peripheral region and the output unit is provided in the central region. Is also good.

[0033]

According to the piezoelectric transformer of the present invention, there is provided a small, low-profile, excellent mass-productivity piezoelectric transformer that uses the primary vibration mode kr whose diameter is expanded on the input side, the output side, or both. It is possible to do.

[Brief description of the drawings]

FIG. 1A is a plan view showing a structure of a piezoelectric transformer according to a first embodiment of the present invention, and FIG.
FIG. 2 is a longitudinal sectional view showing the internal structure of the piezoelectric transformer of FIG.
(C) is a partial enlarged view of (b), and (d) is a stress and displacement distribution diagram of the piezoelectric transformer in the primary vibration mode of (a).

FIG. 2A is a plan view showing a structure of a piezoelectric transformer according to a second embodiment of the present invention, and FIG.
FIG. 2 is a longitudinal sectional view showing the internal structure of the piezoelectric transformer of FIG.
(C) is a partially enlarged view of (b), (d) is a view showing the distribution of stress and displacement of the piezoelectric transformer in the primary vibration mode of (a), and (e) is (a) FIG. 5 is a diagram showing distributions of stress and displacement of the piezoelectric transformer in the third vibration mode.

FIG. 3A is a plan view showing a structure of a piezoelectric transformer according to a third embodiment of the present invention, and FIG.
FIG. 2 is a longitudinal sectional view showing the internal structure of the piezoelectric transformer of FIG.
(C) is a partial enlarged view of (b), and (d) is a stress and displacement distribution diagram of the piezoelectric transformer in the primary vibration mode of (a).

FIG. 4A is a plan view showing a structure of a piezoelectric transformer according to a fourth embodiment of the present invention, and FIG.
FIG. 2 is a longitudinal sectional view showing the internal structure of the piezoelectric transformer of FIG.
(C) is a partial enlarged view of (b), and (d) is a stress and displacement distribution diagram of the piezoelectric transformer in the primary vibration mode of (a).

[Explanation of symbols]

11, 21 Piezoelectric transformer regular octagon plate 31, 41 Piezoelectric transformer square plate 12, 22, 32, 42 Input unit 13, 23, 33, 43 Output unit 14, 34 Insulating region of ceramics 15a, 15b, 25a, 25b, 35a, 35b, 4
5a, 45b Input internal electrodes 16a, 16b, 26a, 26b, 36a, 36b, 4
6a, 46b Output internal electrode

Claims (5)

[Claims] 1. An input section having a plurality of electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked so as to face each other in a thickness direction of a piezoelectric ceramic regular polygon plate, and similarly to face an input section in a thickness direction. An output unit having a plurality of electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked is provided, and between the electrodes in the input unit and the output unit is polarized in the thickness direction of the piezoelectric ceramic regular polygon plate. A piezoelectric transformer characterized by the following. 2. An input section having a plurality of electrodes in which piezoelectric ceramic layers and electrodes are alternately laminated so as to face each other in a thickness direction in a central region of a piezoelectric ceramic regular polygon plate, and has no electrodes outside thereof. An insulating annular region, further comprising an output unit having a plurality of annular electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked so as to face each other outside in the thickness direction, wherein the input unit and the respective electrodes in the output unit are provided. The piezoelectric transformer is characterized in that the space is polarized in the thickness direction of the piezoelectric ceramic regular polygon plate. 3. An output portion having a plurality of electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked so as to face each other in a thickness direction in a central region of a piezoelectric ceramic regular polygon plate, and no electrodes outside the output portion. An insulating annular region, further comprising an input unit having a plurality of annular electrodes in which piezoelectric ceramic layers and electrodes are alternately stacked so as to face each other outside in the thickness direction, wherein the input unit and the output unit include a plurality of annular electrodes. A piezoelectric transformer characterized in that the piezoelectric transformer is polarized in the thickness direction of the piezoelectric ceramic regular polygon plate. 4. The method for driving a piezoelectric transformer according to claim 1, wherein the piezoelectric transformer is driven in a radially expanding primary vibration mode of the piezoelectric ceramic regular polygon plate. 5. The method for driving a piezoelectric transformer according to claim 2, wherein the piezoelectric transformer is driven in a radially expanding primary vibration mode or a radially expanding tertiary vibration mode of the piezoelectric ceramic regular polygon plate. Characteristic driving method of piezoelectric transformer.