JPH11150310A - Piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric transformer which has a low contact resistance and a high conversion efficiency (a small loss) and hardly causes temperature rises. SOLUTION: A piezoelectric transformer is constituted in such a way that a vibrator 11 is formed by laminating rectangular plates for vibrator composed of a piezoelectric ceramic and each carrying input-output internal electrodes 14 and 16 on its surface upon another, and linear connecting sections 18 which become input-output terminals are provided on one side face of the vibrator 11 at the end sections of surfaces 1 on which the node points (of vibration) of the vibrator 11 are formed. In addition, supporting terminals 19 composed of a conductive material are used for the connecting sections 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer utilizing vibration in the length direction of a piezoelectric vibrator and utilizing a k33 mode (a vibration mode in a direction parallel to the direction of an electric field).

[0002]

[Prior Art] Starting with portable televisions and notebook computers,
2. Description of the Related Art With the spread of various portable electronic devices, an AC adapter that receives a commercial AC power supply and outputs DC power has been used to supply DC power to these devices.

A common AC adapter has a common mode choke coil for electromagnetic noise countermeasures sequentially from the input side, a full-wave rectifier circuit, and a smoothing capacitor in parallel with a DC circuit. In the subsequent stage, there is a switching circuit for converting DC to AC. The AC power converted into AC by the switching circuit enters an electromagnetic induction transformer and is converted (generally stepped down) into a predetermined AC voltage. Finally, the AC power is rectified to a predetermined DC power. Is output.

[0004] Among the electronic components used in the AC adapter, an electronic component that is particularly large in volume and that greatly affects the conversion efficiency of the AC adapter is an electromagnetic induction transformer.

On the other hand, demands for higher efficiency, smaller size, lower electromagnetic noise and lower power consumption of AC adapters have been increasing, and a piezoelectric transformer that uses mechanical vibration energy as a conversion medium instead of an electromagnetic induction transformer has been introduced. Is planned.

In order not to impair the conversion efficiency of the piezoelectric transformer, that is, to minimize the conversion loss of the piezoelectric transformer, it is necessary that the output impedance of the piezoelectric transformer and the input impedance of the load match. . The input impedance of various portable electronic devices connected to the output section of the AC adapter is approximately several ohms.
To several tens of ohms. On the other hand, the output impedance R of the piezoelectric transformer is expressed by the following equation by the angular frequency ω (= 2πf) and the output side braking capacitance Cd2.

R = 1 / ωCd2

As an example, Cd2 is 160 nF and f is 1
If it is 20 kHz, R will be 10Ω.

In a piezoelectric transformer for an AC adapter having practical dimensions, in order to secure such a large braking capacity,
A laminated structure of rectangular plates having internal electrodes arranged to face each other is used. In addition, many step-up piezoelectric transformers that have been conventionally used in inverters (DC / AC converters) often have an output of about several watts, and at most have an output of about ten watts at most. In this case, the input voltage is generally 1
00V, the input current is several hundred mA or less, and the output voltage is high, so the output current is only several mA.

[0010]

On the other hand, in the case of a piezoelectric transformer for an AC adapter or a piezoelectric transformer for a DC-DC converter, the output power often reaches several tens of watts, and the input current is several hundred mA. However, since the voltage is lowered on the output side and the voltage becomes several tens of volts, the output current reaches from several hundred mA to 1 A or more.

Thus, despite the large current,
Connecting the external electrode 13 to the connection portion 48 such as a lead wire or a conductive member also serving as a support by point contact (FIG. 4) increases contact resistance, lowers conversion efficiency, and increases temperature rise.

An object of the present invention is to provide a piezoelectric transformer having low contact resistance, high conversion efficiency (low loss), and low temperature rise.

[0013]

SUMMARY OF THE INVENTION The present invention relates to a piezoelectric transformer which is formed by laminating piezoelectric ceramic plates having internal electrodes and converts a voltage using a longitudinal resonance mode. This is a piezoelectric transformer in which a linear connection portion (input / output terminal) is provided at an end of a surface formed by (a point where the displacement is 0).

Further, the present invention is the above-described piezoelectric transformer, wherein the connecting portion uses a supporting terminal made of a conductive material.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, input / output internal electrodes 14, 15, 16, 17 are provided on the surface of a rectangular plate for a vibrator made of a piezoelectric ceramic having a rectangular plate shape [FIGS.
3 (b)], the rectangular plates are laminated to form a vibrator 11,
A linear connecting portion 18 [FIGS. 1, 2, and 3] is formed on the side surface of the vibrator at the end of the surface formed by the (oscillation) node points of the vibrator.
(C)]. The piezoelectric transformer uses a support terminal 19 [FIGS. 1, 2, and 3 (d)] made of a conductive material for the connection portion. The piezoelectric transformer of the present invention is a piezoelectric transformer having a small contact resistance at the terminal lead-out portion, a small loss, and a small temperature rise because the input / output terminals as the connection portions are linear.

[0016]

Embodiments of the present invention will be described below in detail with reference to examples.

(Embodiment 1) FIG. 1 shows a piezoelectric transformer according to a first embodiment of the present invention. FIG. 1A is an explanatory view showing an outline of a piezoelectric transformer, FIG. 1B is an explanatory view showing an internal electrode pattern of a rectangular plate for a vibrator, and FIG. FIG. 1 (d) is an explanatory view provided with a connection portion,
It is explanatory drawing which used the support terminal for the connection part.

As shown in FIG. 1A, the vibrator 11 of the piezoelectric transformer according to the present embodiment is formed by laminating 75 rectangular plates made of piezoelectric ceramics having a thickness of 100 μm. It is 24 mm, 9 mm wide and 7.5 mm thick. External electrodes 12 and 13 for connecting to the linear internal electrodes are provided on the side surface of the vibrator 11.

Then, as shown in FIG. 1B, a rectangular plate is formed on the surface of a rectangular plate for a vibrator (not shown) in the longitudinal direction.
Eight input linear internal electrodes 14 and 16 are arranged in the left half area in the drawing, which is an input part of the equally divided part, and the end of the internal electrode is alternately placed on the side surface of the vibrator alternately. The exposed linear internal electrodes 15 and 1 are exposed in the right half area which is the output section.
Thirty were arranged (some are omitted in the figure), and the ends of the internal electrodes were alternately exposed on the side faces of the vibrator alternately as in the case of input.

The input linear internal electrodes 14 and 16 are made of a silver-palladium alloy and have a line width of 100 μm and a length of 8 mm, and the arrangement pitch is 1.2 mm. The output linear internal electrodes 15 and 17 are also made of a silver-palladium alloy and have a line width of 80 μm and a length of 8 mm, and the arrangement pitch is 320 μm. Then, it was polarized in the direction of arrow 10 (FIG. 1B). Only one set of arrows 10 is shown for the sake of simplicity.

As shown in FIG. 1 (c), in the piezoelectric transformer of the present embodiment, the vibrator has both ends in the longitudinal direction of the vibrator, which are the ends of the surface 1 where the nodes of vibration are formed. A linear connection portion 18 was formed by using a lead wire in two places at a position 1/4 from the center and a total of four places on both side surfaces in parallel with the thickness direction.

As shown in FIG. 1D, a piezoelectric transformer having another connecting portion of the present embodiment is provided with a conductive material at an end of a surface 1 [FIG. 1C] where a node point is formed. The connecting portion is formed by using the supporting terminal 19 made of phosphor bronze.

For comparison, as shown in FIG.
A conventional connection method is used. A lead wire is connected by point contact to two places at 1/4 positions from both end faces in the longitudinal direction of the vibrator 11, a total of four places on both side faces, and a point contact at the center in the thickness direction. 48 was obtained. 12 is an input internal electrode, and 13 is an output external electrode.

The piezoelectric transformers of the present embodiment and the comparative example obtained as described above are supported by using the one-wavelength resonance mode at a position 1/4 from the longitudinal end face of the vibrator. The characteristics of the piezoelectric transformer at an input of 70 Vrms and a load resistance of 13Ω were measured. Table 1 shows the results.

[0025]

(Embodiment 2) FIG. 2 shows a piezoelectric transformer according to a second embodiment of the present invention. FIG. 2A is an explanatory view showing an outline of a piezoelectric transformer, FIG. 2B is an explanatory view showing an internal electrode pattern of a rectangular plate for a vibrator, and FIG. FIG. 2D is an explanatory view in which a connection portion is provided.
It is explanatory drawing which used the support terminal for the connection part.

As shown in FIG. 2A, the vibrator 21 of the piezoelectric transformer according to the present embodiment is formed by laminating 67 rectangular plates made of piezoelectric ceramics having a thickness of 100 μm. It is 24 mm, 6.7 mm wide and 6.7 mm thick. External electrodes 22 and 23 for connecting to the linear internal electrodes are provided on the side surface of the vibrator 21.

Then, as shown in FIG. 2 (b), a rectangular plate is placed on the surface of the rectangular plate for the vibrator (not shown) in the longitudinal direction.
Eight input linear internal electrodes 24 and 26 are arranged in a central area, which is an input portion of the equally divided portions, and the end portions of the internal electrodes are alternately exposed on the side surfaces of the vibrator alternately. The output linear internal electrodes 25,
Fifteen 27 were arranged (partially omitted in the figure), and the ends of the internal electrodes were alternately exposed on the side surfaces of the vibrator alternately as in the case of input.

The input linear internal electrodes 24 and 26 are electrodes made of a silver-palladium alloy and having a line width of 100 μm and a length of 6 mm, and the arrangement pitch is 0.8 mm. The output linear internal electrodes 25 and 27 are also electrodes made of a silver-palladium alloy and having a line width of 80 μm and a length of 6 mm, and the arrangement pitch is 430 μm. Then, it was polarized in the same direction as in Example 1.

As shown in FIG. 2C, in the piezoelectric transformer according to the present embodiment, the vibrator 21 is provided at the end of the surface 1 where the node of vibration is formed. Using a lead wire, a linear connection portion 28 was formed at positions 1/6 from both ends and three positions at the center and a total of six positions on both side surfaces in parallel with the thickness direction.

As shown in FIG. 2D, a piezoelectric transformer having another connecting portion of the present embodiment is provided with a conductive material at an end of a surface 1 [FIG. 2C] where a node point is formed. The connecting portion is formed by using the supporting terminal 29 made of phosphor bronze.

Further, for comparison, the conventional connection method, that is, the position at 1/6 from the both end surfaces in the longitudinal direction of the vibrator and three positions at the center, and a total of six positions on both side surfaces, in the thickness direction, was used. A lead wire was connected to the center by point contact to obtain a piezoelectric transformer (comparative example) as a connection portion.

The piezoelectric transformers of this embodiment and the comparative example obtained as described above are supported at a position 1/6 from the longitudinal end face of the vibrator using the 1.5-wavelength resonance mode. The characteristics of the piezoelectric transformer at an input of 70 Vrms and a load resistance of 21Ω were measured. Table 2 shows the results.

[0034]

(Embodiment 3) FIG. 3 shows a piezoelectric transformer according to a third embodiment of the present invention. 3A is an explanatory view schematically showing a piezoelectric transformer, FIG. 3B is an explanatory view showing an internal electrode pattern of a rectangular plate for a vibrator, and FIG. FIG. 3 (d) is an explanatory view provided with a connection portion,
It is explanatory drawing which used the support terminal for the connection part.

As shown in FIG. 3A, the vibrator 31 of the piezoelectric transformer of this embodiment is formed by laminating 58 rectangular plates made of 100 μm-thick piezoelectric ceramics. It is 24 mm, 5.8 mm wide and 5.8 mm thick. External electrodes 32 and 33 for connecting to the linear internal electrodes are provided on the side surfaces of the vibrator 31.

Then, as shown in FIG. 3 (b), a rectangular plate is placed on the surface of the rectangular plate for the vibrator (not shown) in the longitudinal direction.
Input linear internal electrodes 34 and 36 are provided in each of the two regions at the center, which is the input portion, among the equally divided portions.
The end portions of the internal electrodes are alternately exposed on the side surfaces of the vibrator alternately, and 15 output linear internal electrodes 35 and 37 are provided in the left and right quarters of the output portion. Each of them was arranged (partially omitted in the figure), and the ends of the internal electrodes were exposed on the side surfaces of the vibrator alternately and alternately as in the case of input.

The input linear internal electrodes 34 and 36 are made of a silver-palladium alloy and have a line width of 100 μm and a length of 5 mm, and the arrangement pitch is 1.2 mm. The output linear internal electrodes 35 and 37 are also electrodes made of a silver-palladium alloy and having a line width of 80 μm and a length of 5 mm, and the arrangement pitch is 300 μm. Then, it was polarized in the direction of the arrow 10 (FIG. 3B). Only one set of arrows 10 is shown for the sake of simplicity.

As shown in FIG. 3C, in the piezoelectric transformer according to the present embodiment, the vibrator 31 is provided at the end of the surface 1 where the node point of the vibration is formed. Using a lead wire, a linear connection portion 38 was formed at 1/8 position and 3/8 position from both ends and 4/8 positions and a total of 8 positions on both side surfaces in parallel with the thickness direction.

As shown in FIG. 3D, a piezoelectric transformer having another connection portion of the present embodiment is provided with a conductive material at an end of a surface 1 [FIG. 3C] where a node point is formed. The connecting portion is formed using the supporting terminal 39 made of phosphor bronze.

For comparison, a conventional connection method, ie, a position 1/8 from both end faces in the longitudinal direction of the vibrator and a 3/3
A piezoelectric transformer (comparative example) was obtained by connecting a lead wire to the center in the thickness direction by connecting the lead wires at four positions at eight positions and a total of eight positions on both side surfaces by point contact.

Using the two-wavelength resonance mode, the piezoelectric transformers of the present embodiment and the comparative example obtained as described above are supported at a position 1/8 from the longitudinal end face of the rectangular plate. The characteristics of the piezoelectric transformer at an input of 70 Vrms and a load resistance of 20Ω were measured. Table 3 shows the results.

[0043]

As shown in Tables 1 to 3, the piezoelectric transformer of the present invention can be used in the piezoelectric transformer of the comparative example regardless of the important evaluation items of the piezoelectric transformer, namely, (conversion) efficiency and temperature rise at the time of stable output. It is better than a transformer. That is, the conversion efficiency is improved by 1 to 2%, and the amount of temperature rise is reduced. This indicates that the contact resistance of the connection portion of the piezoelectric transformer of the present invention is low.

[0045]

According to the present invention, a piezoelectric transformer having low contact resistance, high conversion efficiency (low loss), and low temperature rise can be obtained.

[Brief description of the drawings]

FIG. 1 is a view showing a piezoelectric transformer according to a first embodiment of the present invention. FIG. 1A is an explanatory view showing an outline of the piezoelectric transformer.
FIG. 1B is an explanatory diagram showing an internal electrode pattern of the vibrator, FIG. 1C is an explanatory diagram in which a linear connecting portion is provided on the piezoelectric transformer, and FIG. FIG.

FIG. 2 is a view showing a piezoelectric transformer according to a second embodiment of the present invention. FIG. 2A is an explanatory view showing an outline of the piezoelectric transformer.
FIG. 2B is an explanatory view showing an internal electrode pattern of the vibrator, FIG. 2C is an explanatory view in which a linear connecting portion is provided on the piezoelectric transformer, and FIG. FIG.

FIG. 3 is a view showing a piezoelectric transformer according to a third embodiment of the present invention. FIG.
FIG. 3B is an explanatory view showing an internal electrode pattern of the vibrator, FIG. 3C is an explanatory view showing a linear connection portion provided on the piezoelectric transformer, and FIG. FIG.

FIG. 4 is an explanatory view showing a state in which a conventional point contact lead wire is connected to a piezoelectric transformer.

[Explanation of symbols]

Reference Signs List 1 (surface formed by vibration node points) 10 Arrow (indicating polarization direction) 11, 11, 31 (piezoelectric) vibrator 12, 22, 32 (input side) External electrode 13, 23, 33 (output side) External electrodes 14, 16, 24, 26, 34, 36 (input linear) Internal electrodes 15, 17, 25, 27, 35, 37 (output linear) Internal electrodes 18, 28, 38 (linear) Connection 19, 29, 39 Support terminal 48 (conventional) connection

Claims (2)

[Claims] 1. A piezoelectric transformer which is formed by laminating piezoelectric ceramic plates having internal electrodes and converts a voltage using a resonance mode in a longitudinal direction, wherein the piezoelectric transformer is provided at an end of a surface on which a node point of vibration is formed. And a linear transformer provided with a linear connecting portion. 2. The piezoelectric transformer according to claim 1, wherein a support terminal made of a conductive material is used for the connection part.