JPH11266040A - Piezoelectric transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric transformer of a structure, wherein the reduction in mechanical vibration Qm is suppressed by raising the excitation efficiency of a vibrator and decreasing the number of input side lead wires to two wires and the deterioration in the performance of the transformer due to spurious vibrations is inhibited by decreasing the region of the exciting force of the spurious vibrations. SOLUTION: A piezoelectric transformer 10 is provided with a structure, wherein a resonance mode (n=1, 2, 3, and so on) of an order (n) in the lengthwise direction of a piezoelectric ceramic rectangular rod 1 is utilized, groups of linear internal electrodes 7a, 7b, 8a, 8b, 9a and 9b provided in plurality parallel to the widthwise direction within a surface parallel to the lengthwise direction of the rod 1 are laminated on the rod 1 in plural layers in the thickness direction of the rod 1, the end parts, which are exposed on the surfaces of the rod of the electrodes 7a, 7b, 8a, 8b, 9a and 9b are respectively connected with input terminal electrode pair 2 and 2' and output terminal electrode pairs 3a, 3a', 3b and 3b', which are provided on the side surfaces of the rod, so that each electrodes 7a, 7b, 8a, 8b, 9a and 9b become facing electrode with each other one by one, in the lengthwise direction of the rod 1 and the lengths of the electrodes 7a and 7b, which are connected with the electrode pair 2 and 2' on the side surfaces of the rod, are made to be distributed so that the excitation force (the mean value of the section of a vibrator) of the length vibrations of the vibrator is shifted by roughly a 1/4 wavelength from the distribution of the displacement of the vibrator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer having a structure in which a linear internal electrode group is connected to a pair of input terminals and a pair of output terminals using the length vibration of a piezoelectric ceramic rectangular bar. .

[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 have been used to supply DC voltages to these devices. 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.

Recently, the efficiency of AC adapters has been improved,
Demands for miniaturization, reduction of electromagnetic noise, and reduction of power consumption have increased, and various types of piezoelectric transformers have been studied instead of electromagnetic transformers. Furthermore, in order to match the output impedance of the piezoelectric transformer with the load resistance and realize high efficiency of the piezoelectric transformer, it is necessary to increase the braking capacity at the output end. As one solution to these problems, a practical use of an AC adapter using a laminated piezoelectric transformer in which a linear internal electrode group is connected to an input terminal pair and an output pair using the piezoelectric longitudinal effect as shown in FIG. Is being considered.

FIG. 5A is a perspective view showing the structure of a conventional laminated piezoelectric transformer, and FIG. 5B is a perspective view of FIG.
FIG. 2 is a horizontal sectional view of the multilayer piezoelectric transformer shown in FIG. FIG.
As shown in (a), a piezoelectric transformer 50 includes a piezoelectric ceramic rectangular bar (hereinafter, simply referred to as a rectangular bar) 51 formed of a laminate of an internal electrode and a ceramic plate, and one end of the rectangular bar 51 in the longitudinal direction. First external electrodes 52, 52 ', which extend in the vertical direction and are alternately formed at intervals in the longitudinal direction, on both side surfaces, the rectangular rod 51, the central portion in the longitudinal direction, and both sides on the other end side. Second external electrodes 3 formed opposite to each other
a, 3a 'and third external electrodes 3b, 3b'. The first external electrodes 52, 52 'are connected to lead wires 53, 53' by a rectangular bar 51, respectively.
3, 53 'are electrically connected to each other. Lead wires 6a, 6a ', 6b, 6b' are connected to the second and third external electrodes 3a, 3a 'and 3b, 3b', respectively. The lead wires 6a and 6b 'and the lead wire 6a' and the lead wire 6b 'are electrically connected.

The first external electrodes 52, 52 'correspond to the input-side external electrodes, and the second and third external electrodes 3a, 3a
′, 3b, 3b ′ correspond to the external electrodes on the output side, respectively.

As shown in FIG. 5B, first linear internal electrodes 54a and 54b are provided between ceramic plates 11 on which rectangular rods 51 are stacked, near one end in the length direction. And are formed at intervals in the longitudinal direction, and are alternately arranged in the longitudinal direction.
Are connected to the linear internal electrodes 52, 52 ', respectively. The second linear internal electrodes 8a and 8b and the third linear internal electrode are provided at the center in the longitudinal direction between the stacked ceramic plates 11 of the rectangular rods 51 and at the other end in the longitudinal direction. Electrodes 9a, 9
b are formed respectively. Second linear internal electrodes 8a, 8
b are formed in parallel in a staggered manner in the width direction from one side and the other side of the rectangular bar 51 toward the respective opposing sides. Both the second linear internal electrodes 8a on one side and the second linear internal electrodes 8b on the other side are formed to have substantially the same length. The ends of the respective second linear internal electrodes 8a are connected to the second external electrode 3a at one side of the rectangular rod 51, and the ends of the second linear internal electrodes 8b are connected to the rectangular rod 51. On the other side is connected to the second external electrode 3a '.

The third linear internal electrodes 9a and 9b are also
A plurality of rectangular bars 51 are formed in parallel in a staggered manner in the width direction from one side and the other side of the other end in the length direction toward the respective opposing sides. Both the second linear internal electrodes 9a on one side and the second linear internal electrodes 9b on the other side are formed to have substantially the same length. The ends of each of the second linear internal electrodes 9a are connected to the third external electrode 3b at one side of the rectangular rod 51, and the ends of the third linear internal electrodes 9b are connected to the rectangular rod. The other side of 51 is connected to the third external electrode 3a '.

[0008]

However, FIG.
On the input side or output side of the laminated piezoelectric transformer 50 shown in FIGS. 3A and 3B, the excitation is performed uniformly in the length direction, and the excitation efficiency is not the best. Also,
Since the pitch of the input-side linear internal electrodes is large in order to obtain a matching between the transformation ratio of the input / output voltage and the load resistance, as shown in FIG. In order to connect the lead wires 3 to each of the side external electrodes, the number of lead wires is large. Due to the above, there is a disadvantage that the mechanical vibration quality factor Qm of the vibrator is reduced.

In the conventional laminated piezoelectric transformer 50, spurious vibrations in the thickness and width directions are excited near the resonance frequency of the length vibration. Since the drive circuit of the AC adapter controls the frequency with respect to changes in input voltage and load resistance, these spurious vibrations have the disadvantage of deteriorating the performance of the piezoelectric transformer.

Therefore, a technical problem of the present invention is to improve the excitation efficiency of the vibrator and to reduce the number of lead wires on the input side to two.
By reducing the number of books, the reduction of mechanical vibration Qm is suppressed,
It is another object of the present invention to provide a piezoelectric transformer that suppresses performance degradation of a piezoelectric transformer due to spurious vibration by reducing a region of an exciting force of spurious vibration.

[0011]

According to the present invention, an nth-order resonance mode in the length direction of a piezoelectric ceramic rectangle (however,
n is a positive integer), and in the piezoelectric ceramic rectangle, a plurality of linear internal electrode groups provided in parallel in the width direction in a plane parallel to the length direction are stacked in a plurality of layers in the thickness direction. And
The end of the linear internal electrode exposed on the side is connected to the input terminal electrode pair and the output terminal electrode pair on the side so that one end at a time in the length direction becomes the counter electrode. Value) and the displacement distribution are shifted by about 1/4 wavelength.
A piezoelectric transformer having a structure in which the lengths of the linear internal electrodes connected to the input terminal electrode pairs on the side surfaces are distributed is obtained.

Further, according to the present invention, in the piezoelectric transformer, the distribution of the excitation stress (average value of the cross section) of longitudinal vibration and the distribution of displacement on the input side and the output side are shifted by about 1/4 wavelength. A piezoelectric transformer having a structure in which the lengths of the linear internal electrodes connected to the input and output terminal electrode pairs are distributed.

[0013]

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

FIG. 1A is a perspective view showing a piezoelectric transformer according to a first embodiment of the present invention. FIG. 1B is a sectional view showing an internal electrode pattern of the piezoelectric transformer of FIG. 1A. FIG. 1C is a diagram showing the displacement distribution of the longitudinal vibration and the distribution of the excitation stress in FIG.

[0015] As shown in FIG.
Reference numeral 0 denotes a piezoelectric ceramic rectangular bar (hereinafter, simply referred to as a rectangular bar) 1 formed of a laminate of an internal electrode and a ceramic plate, and one end, the center, and the other end of both sides of the rectangular bar 1. The first external electrodes 2 and 2 ', the second external electrodes 3a and 3a', and the third external electrodes 3b and 3b 'are formed. First to third external electrodes 2, 2 ', 3
a, 3a ', 3b, 3b' are respectively connected to lead wires 5, 5 ', 6a, 6a at nodes 4a, 4b, 4c of vibration of the rectangular bar 1.
, 6b and 6b 'are connected respectively. The lead wire 6a, the lead wire 6b and the lead wire 6a 'are electrically connected to the lead wire 6b', respectively. The first external electrodes 2, 2 'correspond to the input side, and the second and third external electrodes 3a, 3a', 3b, 3b 'correspond to the output side external electrodes, respectively.

As shown in FIG. 1 (b), between the laminated ceramic plates 11 of the rectangular bar 1, near the one end in the length direction, at the center in the length direction, and at the other end in the length direction. Is the first
, The second linear internal electrodes 8a, 7b,
8b and third linear internal electrodes 9a and 9b are formed respectively.

The first linear internal electrodes 7a and 7b are alternately formed in parallel with each other in the width direction from one side and the other side of the rectangular bar 1 to the opposite sides. One side one
Both the group of linear internal electrodes 7a and the group of linear internal electrodes 8b on the other side have a length that is the longest at the center in the length direction, as will be described in detail with reference to FIG. It is formed to have a distribution of height. The ends of the first linear internal electrodes 7a are connected to the first external electrode 2 at one side of the rectangular bar 1, and the ends of the linear internal electrodes 7b are connected to the other side of the rectangular bar 1. Is connected to the first external electrode 2 ′.

The second linear internal electrodes 8a and 8b are
A plurality of rectangular bars 1 are formed alternately in parallel in the width direction from one side and the other side to the respective opposite sides. Both the second linear internal electrodes 8a on one side and the second linear internal electrodes 8b on the other side are formed to have substantially the same length. The ends of each of the second linear internal electrodes 8a are connected to the second external electrode 3a at one side of the rectangular rod 1, and the ends of the second linear internal electrodes 8b are connected to the rectangular rod 1a. On the other side is connected to the first external electrode 3a '.

The third linear internal electrodes 9a and 9b also
A plurality of rectangular bars 1 are formed alternately in parallel in the width direction from one side and the other side of the other end in the length direction toward the respective opposing sides. Both the second linear internal electrodes 9a on one side and the second linear internal electrodes 9b on the other side are formed to have substantially the same length. The ends of each of the second linear internal electrodes 9a are connected to the third external electrode 3b at one side of the rectangular rod 1, and the ends of the third linear internal electrodes 9b are connected to the rectangular rod. One other side is connected to the third external electrode 3a '.

As shown in FIG. 1C, the piezoelectric transformer 1
In the case of 0, the length in the width direction of the input-side internal electrodes 7a and 7b shown in FIG. 1B is designed so that the excitation stress (average value of the cross section) matches the displacement distribution of the longitudinal vibration.

Further, as shown in FIG. 1B, the number of stacked electrodes in the length direction of the input side electrode is increased to 12 layers.

In general, it is known that when the excitation stress of a certain vibration mode and the displacement distribution of the mode are shifted by 1/4 wavelength, this vibration can be efficiently excited.

Therefore, it is conceivable that the performance of the piezoelectric transformer using the vibrator shown in FIG. 1 is improved.

Further, as shown in FIG. 1B, the pitch of the internal electrodes 7a and 7b on the input side is reduced, so that the pattern of the internal electrodes alternately exposed on the side surfaces can be used every other one. . Thus, as shown in FIG. 1A, the internal electrodes are connected by a pair of external electrodes 2 and 2 ', thereby reducing the number of lead wires. As a result, it is possible to suppress a decrease in mechanical vibration Qm of the vibrator due to the lead wire.

Further, in the internal electrode pattern on the input side as shown in FIG. 1B, the region where the excitation force of the spurious vibration due to the piezoelectric transverse effect exists is reduced, and the spurious vibration which degrades the performance of the piezoelectric transformer is suppressed. Can be.

Next, a specific example of a laminated piezoelectric transformer having internal electrodes as shown in FIG. 1B will be described. The dimensions of the transformer are 25 mm in length, 6 mm in width, and 6 mm in thickness. A third-order resonance mode in the length direction is used. The internal electrode pattern of the present invention is arranged on the input side, which is divided into three equal parts in the length direction of the rectangle 1. On the input side, 13 first linear internal electrodes 7a and 7b using a silver-palladium alloy are arranged with a line width of 100 μm, a pitch of 0.6 mm, and a length as shown in FIG.
It is alternately exposed on the side every other book. On the output side, a linear internal electrode made of the same silver-palladium alloy
Thirteen m, pitch 0.6 mm, length 5.9 mm are arranged, and every other one is alternately exposed to the side.

FIG. 2 is a partially enlarged sectional view schematically showing the internal electrode pattern of FIG. 1B. As shown in FIG.
Sixty plane patterns are stacked in the thickness direction at intervals of 100 μm. External electrodes as shown in FIG. 1A are arranged on each side surface of the input / output side to connect a plurality of laminated linear internal electrodes. The direction of polarization 7 is indicated by the arrow in FIG. The nodes 4a, 4a 'of the vibration of the rectangular bar 1
Take out the lead wires 4b, 4b ', 4c, 4c'.

FIG. 3 shows the capacitance ratio γ of the input side when the internal electrode pattern on the input side according to the embodiment of the present invention is used and when the internal electrode pattern of the related art shown in FIG. 5 is used.
_1s / γ _1o shows the characteristics of the number of layers n ₁ on one input side. Also, FIG.
Change in force coefficient due to change in internal electrode pattern A _1S / A
_{10 The} number n ₁ of stacked layers on one input side is also shown. As a result, FIG.
When the number of layers is large as compared with the conventional structure, the use of the internal electrode pattern on the input side according to the first embodiment of the present invention makes it possible to prevent the capacity ratio on the input side from deteriorating and increase the force coefficient. I understand.

Table 1 below shows the input-side transducer constants when the input-side lamination number is 12. In Table 1, f _r1 is the input-side resonance frequency, C _d1 is the input-side braking capacity, A ₁ is the input-side force coefficient, γ ₁ is the input-side capacity ratio, Q
_m1 is the input-side mechanical oscillation quality factor, equivalent series resistance R ₁ is input, L ₁ is the input-side equivalent series inductance, C _a1
Is the equivalent series capacitance on the input side.

[0030]

[Table 1]

It can be seen from Table 1 that the mechanical vibration Qm is increased by using the internal electrode pattern on the input side according to the first embodiment of the present invention.

Next, a second embodiment of the present invention will be described.

FIG. 4A is a diagram showing an internal electrode pattern of a multilayer piezoelectric transformer according to a second embodiment of the present invention. FIG. 4B is a diagram showing a vibration pattern of the multilayer piezoelectric transformer of FIG. 4A.

As shown in FIGS. 4A and 4B,
The input side and the output side use the same internal electrode pattern as the pattern of the first linear internal electrodes 7a and 7b according to the first embodiment.

That is, the first linear internal electrodes 13a, 13b
Are formed in parallel with each other in the width direction from one side and the other side of the rectangular bar 1 toward the respective opposite sides.
Both the first linear internal electrodes 13a on one side and the linear internal electrodes 13b on the other side are the longest at the center in the longitudinal direction, that is, the excitation stress of the longitudinal vibration (the average value of the cross section) ) Is formed so as to have a length distribution such that the displacement distribution of the length vibration is shifted by about 1/4 wavelength. The ends of the first linear internal electrodes 13a are connected to the first external electrode 2 at one side of the rectangular bar 1, and the ends of the linear internal electrodes 13b are connected to the other side of the rectangular bar 1. Is connected to the first external electrode 2 ′.

Further, the second linear internal electrodes 14a, 14b
Are formed in parallel with each other in the width direction from one side and the other side of the rectangular bar 1 toward the respective opposite sides.
Both the second linear internal electrode group 14a on one side and the second linear internal electrode group 14b on the other side are the longest at the center in the length direction, that is, the excitation stress of the longitudinal vibration (cross section) Average)
Is formed so as to have a length distribution such that the displacement distribution of the length vibration deviates by approximately 1/4 wavelength. The ends of the respective second linear internal electrodes 14a are connected to the second external electrode 3a at one side of the rectangular bar 1, and the second linear internal electrodes 14a are connected to each other.
b are connected to the first external electrode 3 on the other side of the rectangular bar 1.
a '.

Further, the third linear internal electrodes 15a, 15b
Also, from one side and the other side of the other end in the length direction of the rectangular bar 1,
A plurality is formed alternately in parallel in the width direction toward the respective opposing sides. Both the second linear internal electrodes 15a on one side and the second linear internal electrodes 15b on the other side are the longest at the center in the length direction, that is, the excitation stress (length section) Average value) is that the length vibration displacement distribution is almost 1/4
It is formed so as to have a distribution of lengths that are shifted in wavelength.

The ends of each of the second linear internal electrodes 15a are connected to the third external electrode 3b at one side of the rectangular bar 1, and the ends of the third linear internal electrodes 15bb are connected to each other. The other side of the rectangular bar 1 is connected to the third external electrode 3a '.

Next, a specific example of a laminated piezoelectric transformer having internal electrodes as shown in FIG. length,
The piezoelectric transformer 20 having a width and a thickness of 25 mm, 6 mm, and 6 mm was manufactured. The piezoelectric transformer 20 utilizes a third-order resonance mode in the length direction. On the input side, nine linear internal electrodes using a silver-palladium alloy were arranged at a line width of 100 μm and a pitch of 1.0 mm, as shown in FIG.
It was exposed to the side alternately in the book. Silver on the output side
A linear internal electrode made of palladium alloy has a line width of 100μ.
M, pitch 0.5 mm, 19 lines were arranged, and every other line was alternately exposed to the side surface. 4 are stacked in the thickness direction at intervals of 100 μm. An external electrode as shown in FIG. 4A is arranged on each side surface on the input / output side to connect a plurality of laminated linear internal electrodes. The direction of polarization and the method of taking out the lead wire were the same as in the first embodiment.

Table 2 below shows the maximum efficiency ηmax, the temperature rise ΔT, the efficiency ηs when spurious vibration occurs, and the temperature rise ΔTs when the piezoelectric transformer 20 is driven by a sine wave voltage.

For comparison, the performance of a conventional laminated piezoelectric transformer having the same dimensions is also shown in Table 2 below. In Table 2, ηmax is the maximum efficiency of the transformer, ηs is the efficiency when spurious vibration occurs, ΔT is the temperature rise of the transformer, and ΔTs is the temperature rise when spurious vibration occurs.

[0042]

[Table 2]

From Table 2 above, it can be seen that the use of the internal electrode pattern according to the second embodiment of the present invention improves the efficiency and suppresses the performance deterioration due to spurious vibration.

In the above embodiment, the multilayer piezoelectric transformer using the third mode in the length direction has been described. However, the same effect can be expected in the nth mode (where n is a positive integer). .

[0045]

As described above, according to the present invention, the mechanical vibration Qm and the force coefficient on the input side are increased, and the influence of spurious vibration is reduced.

Therefore, according to the present invention, it has become possible to obtain a piezoelectric transformer having higher efficiency, easier control, and better temperature characteristics.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a piezoelectric transformer according to a first embodiment of the present invention. (B) is a sectional view showing an internal electrode pattern of the piezoelectric transformer of (a). (C)
FIG. 3A is a diagram showing a displacement distribution of length vibration and a distribution of excitation stress of the piezoelectric transformer in FIG.

FIG. 2 is a partially enlarged sectional view schematically showing an internal electrode pattern of FIG. 1 (b).

A case of using the internal electrode patterns according to embodiments of the present invention; FIG, laminated on the input side of the capacitance ratio gamma _1s / gamma _1o first input side in the case of utilizing the conventional internal electrode pattern shown in FIG. 5 the number n ₁ characteristic diagrams showing respectively.

FIG. 4A is a diagram illustrating an internal electrode pattern of a multilayer piezoelectric transformer according to a second embodiment of the present invention.
(B) is a figure which shows the vibration pattern of the laminated piezoelectric transformer of (a).

FIG. 5A is a perspective view showing the structure of a conventional multilayer piezoelectric transformer. (B) is a horizontal sectional view of the multilayer piezoelectric transformer shown in (a).

[Explanation of symbols]

 1,51 rectangular bar 2,2 'first external electrode 3a, 3a' second external electrode 3b, 3b 'third external electrode 4a, 4b, 4c node of vibration 5,5', 6a, 6a ', 6b, 6b 'Lead wire 7a, 7b First linear internal electrode 8a, 8b Second linear internal electrode 9a, 9b Third linear internal electrode 10, 20, 50 Piezoelectric transformer 11 Ceramic plate 13a, 13b 1 linear internal electrode 14a, 14b second linear internal electrode 15a, 15b third linear internal electrode 52, 52 'first external electrode 53, 53' lead wire 54a, 54b first linear internal electrode

Claims (2)

[Claims] 1. An n-th order resonance mode (where n is a positive integer) in a length direction of a piezoelectric ceramic rectangle is used, and the piezoelectric ceramic rectangle is provided in a plane parallel to the length direction. A plurality of linear internal electrode groups provided in parallel in the width direction are laminated in a plurality of layers in the thickness direction, and the side surfaces are so arranged that the ends of the linear internal electrodes exposed on the side surface become the counter electrodes one by one in the length direction. The length of the linear internal electrode connected to the input terminal electrode pair on the side surface is connected to the input terminal electrode pair and the output terminal electrode pair, and the distribution of the excitation stress and displacement of the longitudinal vibration is shifted by about 1/4 wavelength. A piezoelectric transformer, characterized by having a structure in which the distribution is distributed. 2. The pair of input and output terminal electrodes on the side surface of the piezoelectric transformer according to claim 1, wherein the distribution of the excitation stress and the displacement of the longitudinal vibration is shifted by about 1/4 wavelength on the input side and the output side. A piezoelectric transformer having a structure in which the lengths of linear internal electrodes connected to the piezoelectric transformer are distributed.