JP2002141571A - Piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric transformer of small capacitance ratio, large braking capacity, and large electro-mechanical coupling coefficient. SOLUTION: A laminated piezoelectric transformer is provided where an internal electrode and a ceramics layer are alternately laminated in thickness direction for both input and output parts by utilizing the resonance mode of a piezoelectric ceramics square plate. Here, the ratio between a length direction dimension A and a width direction dimension B of the square plate is 2:1.

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 a piezoelectric transverse effect on both an input side and an output side.

[0002]

2. Description of the Related Art In recent years, demand for a piezoelectric transformer as a power source for a liquid crystal backlight of a notebook personal computer has been rapidly increasing. This is because in the conventional electromagnetic inverter, various problems arise in order to achieve a high voltage of several hundred volts from a DC voltage of a dry cell at the same time as a thinning of several mm.

[0003] By the way, an inverter that boosts voltage to an extremely high voltage is rather special in a power supply, and when applying a piezoelectric transformer to another general power supply, impedance matching with a load is important in terms of efficiency. It becomes. For example, the input impedance of various portable electronic devices connected to the output section of the AC adapter is about several Ω to several Ω.
It is about 0Ω. Output impedance of the piezoelectric transformer can be determined as the frequency omega (= 2 [pi] f) and the output-side damping capacitance C _d2 by (1).

R = 1 / ωC _d2 (1)

For example, when R = 60Ω and f = 120 kHz, C _d2 = 22.1 nF. Although the output side braking capacity C _d2 of the inverter transformer is several tens of pF, a three-digit larger braking capacity is required. The laminated piezoelectric transformer using the longitudinal resonance mode of the piezoelectric ceramic rectangular plate using the piezoelectric piezoelectric effect has a large capacitance because the output section has a structure in which square internal electrodes are laminated. This is one of the structures that are expected to be applied to applications with relatively small load impedance as described above.

[0006]

However, a comparison between the case where piezoelectric lateral effects are used and the case where piezoelectric longitudinal effects are used using piezoelectric ceramics shows that the ratio of electric mechanical energy to mechanical vibration energy Because the coupling coefficient is about half, in high power transmission,
There was a disadvantage that the efficiency was reduced.

An object of the present invention is to solve the above problems and to provide a piezoelectric transformer having a small capacity ratio, a large braking capacity, and a large electromechanical coupling coefficient.

[0008]

According to the present invention, there is provided a laminated piezoelectric transformer in which an internal electrode and a ceramic layer are alternately laminated in the thickness direction at both an input portion and an output portion using a resonance mode of a piezoelectric ceramic rectangular plate. In the said rectangular plate,
A piezoelectric transformer, wherein the ratio of the length dimension to the width dimension is 2: 1.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a piezoelectric transformer according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing an outline of a piezoelectric transformer according to the present invention. FIG. 2 is a plan view showing an outline of the piezoelectric transformer according to the present invention. The dimensions of the piezoelectric transformer of the present invention are 30 mm in length, 15 mm in width, and 4.0 mm in thickness. As shown in FIG. 1, the ratio of the length dimension A to the width dimension B is 2: 1. As shown in FIG. 2, the rectangular plate is divided into two equal parts in the length direction, one of which is an input unit 12 and the other is an output unit 13. Ceramic insulating part 14 having a thickness of 0.3 mm
Are formed.

FIG. 3 is a plan view showing an internal electrode pattern of the piezoelectric transformer according to the present invention. FIG. 4 is a cross-sectional view showing a laminated state of the piezoelectric transformer according to the present invention. FIG.
FIG. 3 is a perspective view illustrating an electrode outlet of the piezoelectric transformer according to the present invention.

As shown in FIG. 3, on the sheet shown in FIG. 3A, an input internal electrode 15a forming an input section is arranged, and an output internal electrode 15b forming an output section is arranged. In the sheet of FIG. 3B, an input internal electrode 16a forming an input unit is arranged, and an output internal electrode 16b forming an output unit is arranged. FIG.
The sheet of FIG. 3 (c) includes the output internal electrode 15b, FIG.
The output internal electrodes 16b are arranged on the sheet (d). When these sheets of FIGS. 3A to 3D are stacked, the outlets of the respective electrodes are alternately exposed on the side surfaces every other one.

As shown in FIG. 4, the input unit 12 and the output unit 1
3 are polarized in opposite directions to each other, with one layer in the thickness direction. The input unit 12 has three layers, and the output unit 13 has 10 layers.
It has a layered structure of layers.

The input internal electrodes 15a and 16a in FIG.
As shown in FIG. 5, each is connected to the side external electrodes 17a and 18a for applying an input signal, and
5b and 16b are side external electrodes 17 for taking out output.
b, 18b.

The performance was evaluated using the piezoelectric transformer of the present invention having such a structure. Polarization is 1.5 kV / mm in silicone oil at 165 ° C for both input and output.
The electric field strength was as follows.

Similarly, as a conventional example, a piezoelectric transformer having a length of 30 mm, a width of 10 mm, and a thickness of 4.0 mm was prepared.
The braking capacity and the capacity ratio were compared between the piezoelectric transformer of the present invention and the conventional piezoelectric transformer. Table 1 shows the results.

[0017]

[Table 1]

From Table 1, it can be seen that the capacitance ratio in the conventional example was 19 on both the input side and the output side, but was improved to 4.8 by the present invention.

[0019]

As described above, according to the present invention,
By using the length vibration mode of the rectangular plate, it is possible to provide a piezoelectric transformer having a small capacitance ratio, a large braking capacity, and a large electromechanical coupling coefficient.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an outline of a piezoelectric transformer according to the present invention.

FIG. 2 is a plan view showing an outline of a piezoelectric transformer according to the present invention.

FIG. 3 is a plan view showing an internal electrode pattern of the piezoelectric transformer according to the present invention.

FIG. 4 is a sectional view showing a laminated state of a piezoelectric transformer according to the present invention.

FIG. 5 is a perspective view illustrating an electrode outlet of a piezoelectric transformer according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 12 Input part 13 Output part 14 Insulation part 15a, 16a Input internal electrode 15b, 16b Output internal electrode 17a, 18a Side external electrode 17b, 18b Side external electrode A Length dimension B Width dimension

Claims (1)

[Claims] 1. A laminated piezoelectric transformer using a resonance mode of a piezoelectric ceramic rectangular plate and alternately laminating internal electrodes and ceramic layers in the thickness direction at both an input portion and an output portion, wherein the rectangular plate has a long length. A piezoelectric transformer, wherein the ratio of the width dimension to the width dimension is 2: 1.