JP3401663B2 - 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 that uses the k33 mode on the input side or the output side or both while using the length vibration of a rectangular plate.

[0002]

2. Description of the Related Art With the widespread use of various portable electronic devices such as portable televisions and notebook 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. There is. A circuit diagram of a general AC adapter is shown in FIG. On the input side, there is a common mode choke coil to prevent electromagnetic noise, then there is a full-wave rectifier circuit, and then there is a smoothing capacitor in parallel with the DC circuit to prevent large instantaneous disconnections. Next, there are switches S1 and S2 for converting DC into AC, and the AC voltage converted here enters an electromagnetic transformer and is converted into a predetermined AC voltage. Finally, a switching type AC adapter rectifies this AC voltage and outputs a predetermined DC voltage. Among the electronic components used in the AC adapter, the electromagnetic transformer has a large volume and affects the conversion efficiency of the AC adapter. Recently, high efficiency, small size and low profile of AC adapter,
With the increasing demands for reduction of electromagnetic noise and low power consumption, a piezoelectric transformer that uses mechanical vibration energy as a conversion medium has been studied instead of an electromagnetic transformer. Although the impedance matching between the output impedance of the piezoelectric transformer and the load is important for the efficiency of the piezoelectric transformer, the input impedance of various portable electronic devices connected to the output part of the AC adapter is about several Ω to several tens Ω. The output impedance of the piezoelectric transformer is at each frequency ω (= 2πf)
And the output side braking capacity Cd2, it is obtained as in the equation (1).

R = 1 / ωCd2 (1) As an example, when R = 10Ω and f = 120 kHz, Cd2 = 160 nF.

In order to secure such a large braking capacity in a piezoelectric transformer for an AC adapter having a practical size, it is necessary to have a laminated structure with counter internal electrodes.

[0005]

However, in order to employ impedance-matching internal electrodes on the output side in order to achieve impedance matching, the stacking direction of the internal electrodes and the ceramics coincides with the length direction of the piezoelectric ceramic rectangular plate ( There are two possible methods: (k33) and (k31) method of matching in the thickness direction.

Since the former is expected to have a higher electromechanical coupling coefficient than the latter, the energy conversion efficiency of the piezoelectric transformer becomes high. However, problems remain in terms of mechanical strength.

That is, the noble metal, which is the internal electrode layer, and the piezoelectric ceramic do not chemically react with each other, but are mechanically fixed to each other. When driven at the resonant frequency in the length direction,
There is a possibility of destruction from the interface between the internal electrode and the ceramics. Further, stacking in the length direction has a large number of stacks, which is a problem in terms of cost. Moreover, the internal electrode is 1 on the side surface of the rectangular plate.
Another strength problem arises when exposed layer by layer and connected by external electrodes. When every other layer is exposed on the side surface, a portion indicated as an inactive portion in FIG. 1A is not polarized near the side surface. On the other hand, when the active portion is polarized, it extends in the lengthwise direction, so that the vicinity of the inactive portion is shown in FIG.
It will be deformed as shown in, and a large distortion will occur. The residual stress caused by this is
It is generally known that it corresponds to the tensile strength of a material.

The objects of the present invention are as follows.

By providing the internal electrodes as linear electrodes instead of surface electrodes and by laminating in the thickness direction of the piezoelectric transformer rectangular plate, a piezoelectric transformer having high mechanical strength, good energy conversion efficiency, and low cost is provided. To do.

To prevent a decrease in strength in the inactive portion while obtaining a high coupling coefficient by using a plane electrode or a linear electrode.

To prevent a decrease in strength in the inactive portion while obtaining a high coupling coefficient by using k33.

[0012]

In order to solve the above problems, in a piezoelectric transformer utilizing a one-wavelength resonance mode in the length direction of a piezoelectric ceramic rectangular plate, a piezoelectric ceramic
On at least one portion of which is bisected in the longitudinal direction of the click rectangular plate, double by parallel and stacked linear electrode in the thickness direction in the width direction in the multiple plane orthogonal to the longitudinal direction
A structure in which several layers of linear internal electrodes are laminated in the lengthwise direction, and a group of linear internal electrodes of these multiple layers are alternately exposed in the lengthwise direction on two side surfaces of the piezoelectric ceramic rectangular plate. Piezoelectric transformer with a structure characterized by

[0013] In the piezoelectric transformer and perpendicular to the longitudinal direction linear internal electrode group provided a plurality of layers of the piezoelectric cell
A piezoelectric transformer having a structure characterized by being exposed on two side surfaces of a lamic rectangular plate was examined.

In order to solve the above problems, in a piezoelectric transformer utilizing a one-wavelength resonance mode in the lengthwise direction of a piezoelectric ceramic rectangular plate, at least one of the two halves of the piezoelectric ceramic rectangular plate in the lengthwise direction. in part, or in parallel in the width direction in the plane of the number of multiple orthogonal to the length <br/> direction
Multiple layers linear within by stacking in the thickness direction of the linear electrodes One
The part electrode is laminated in the length direction structure of multiple layers
Linear internal electrode group, the exposed on two sides of the piezoelectric ceramic rectangular plate, are connected by further said piezoelectric ceramic rectangular plate plurality of side electrodes parallel to the thickness direction provided on the side surface, these thickness direction Parallel side electrodes are 1 in the length direction
The piezoelectric ceramic
(C) A piezoelectric transformer characterized in that it is connected to the side surface of the rectangular plate, the upper and lower surfaces, or both end surfaces was also examined.

[0015]

With the piezoelectric transformer of the present invention, the strength can be ensured by using k33 on the input side, the output side, or both. Further, by pulling out the linear electrodes on the side surfaces of the rectangular plate and collecting them on the side surfaces, the upper and lower surfaces, or both end surfaces, it becomes possible to lead at the node point of vibration (the portion where the amplitude is zero), and the reliability can be improved. .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A piezoelectric transformer according to an embodiment of the present invention will be described with reference to the drawings with reference to the accompanying claims.

[0017]

EXAMPLE 1 FIG. 1 is a schematic perspective view of the vibrator structure of a piezoelectric transformer according to claim 1 of the present invention. Dimension is 32m long
m, width 10 mm, and thickness 6 mm. Eight linear internal electrodes 14 and 16 using a silver-palladium alloy are arranged in a line width of 100 μm, a length of 9 mm, and a pitch of 2 mm in a partial area of about a half of the piezoelectric ceramic vibrator rectangular plate 11 which is an input portion. , Every other is exposed on the side alternately. In the remaining half of the rectangular plate which is the output part, 30 linear internal electrodes 15 and 17 also made of a silver-palladium alloy are arranged with a line width of 80 μm, a length of 8 mm and a pitch of 500 μm. Alternately exposed to the side. The plane pattern shown in FIG. 1 (B). The arrow in the figure indicates the polarization direction. Further, 50 layers of this plane pattern are laminated in the thickness direction at intervals of 120 μm. Further, external electrodes 12 and 13 for connecting to a plurality of stacked linear internal electrodes are present on the side surfaces of each of the input / output portions. Table 1 shows the optimum load calculated from the resonance frequency of the prototype piezoelectric transformer, the oscillator constants on the input and output sides, and the braking capacity on the output side. Also, using the one-wavelength resonance mode of the prototype piezoelectric transformer, the input 70Vrms, supporting the position of ¼ from the end face in the length direction of the rectangular plate,
The piezoelectric transformer characteristic was measured when the load resistance was 10Ω. The results are also shown in Table 1.

[0018]

[Table 1]

[Embodiment 2] FIG. 2 shows a schematic perspective view of a vibrator structure of a piezoelectric transformer according to a second embodiment of the present invention. The dimensions are 32 mm in length, 10 mm in width, and 6 mm in thickness. An input linear internal electrode 24 made of a silver-palladium alloy is provided in a partial area of about a half of the piezoelectric transformer vibrator rectangular plate 21 which is an input part, with a line width of 100 μm and a length of 8 mm.
Eight pieces are arranged with a pitch of 2 mm, and all are exposed on two side surfaces (front and rear side surfaces). In the other half of the area of the rectangular plate 21 which is the output section, 30 linear internal electrodes 26 and 27 also made of a silver-palladium alloy are arranged with a line width of 80 microns, a length of 9 mm and a pitch of 500 μm. It is exposed to the side alternately every other line. This plane pattern is shown in FIG.
It shows in (B). This plane pattern is 120μ in the thickness direction.
50 layers are laminated at m intervals. A plurality of linear internal electrodes 26 and 27 are stacked on each side surface of the output section.
An output side surface electrode 25 is provided as an external electrode for connecting to. On the other hand, on the input side, the input side electrode 22 and the input side electrode 23, in which every other linear internal electrode 24 is selected, are provided, and the electrodes are put together on the upper surface of the rectangular plate 21. Table 1 shows the optimum load calculated from the resonance frequency of the prototype piezoelectric transformer, the oscillator constants on the input and output sides, and the braking capacity on the output side. In addition, the one-wavelength resonance mode of the prototype piezoelectric transformer is used to support a position ¼ from the end face in the length direction of the rectangular plate 21 and input 70 Vrms.
The piezoelectric transformer characteristics were measured when the load resistance was 10Ω.
The results are also shown in Table 1.

According to this, the piezoelectric transformer of the second embodiment is
The capacitance ratio on the input side is 7 compared to the piezoelectric transformer of the first embodiment.
However, in the case of the piezoelectric transformer of the second embodiment, since the piezoelectrically inactive portion in the vicinity of the external electrode does not exist on the input side, the oscillator characteristic is improved. It is thought that it was done.

Example 1 employing a linear internal electrode group
The bending strength of the piezoelectric transformer is larger than that when the planar electrode is adopted, and in the case of the piezoelectric transformer of the second embodiment, the inactive portion that becomes the starting point of the piezoelectric transformer breakdown at the input portion during polarization or driving. It can be seen that the strength is further improved from the disappearance of. In this example, the linear internal electrodes 24 exposed on the two side surfaces are arranged only in the input section, and the output section has the same structure as in Example 1 (claim 1), but a method such as screen printing or sputtering is used. It goes without saying that it can also be applied to the output section, and in that case, the strength, oscillator characteristics, etc. can be improved.

[Embodiment 3] The vibrator according to claim 3 (Embodiment 3) of the piezoelectric transformer of the present invention in FIG. 4 has dimensions of 32 mm in length, 10 mm in width, and 6 mm in thickness. Eight linear internal electrodes 44 using a silver-palladium alloy with a line width of 100 microns, a length of 9 mm, and a pitch of 2 mm are arranged in about half the area of the rectangular plate 41 which is the input section, and are exposed on two side surfaces. is doing. In the remaining approximately half of the rectangular plate 41, which is the output section, 30 linear internal electrodes 46 , which are also made of a silver-palladium alloy, are arranged with a line width of 100 microns, a length of 8 mm, and a pitch of 500 mm. Alternately exposed to the side. This plane pattern is shown in FIG. The arrow in the figure indicates the polarization direction.

Further, this plane pattern is 12 in the thickness direction.
50 layers are laminated at intervals of 0 μm. These linear internal electrodes 44 are connected by a plurality of linear electrodes (input side electrodes) 42, 43 provided in the side surface of the rectangular plate 41 and parallel to the thickness direction, and every other one in the length direction. It is drawn out so as to have the same polarity and is collected on the upper surface of the rectangular plate 41. Using the one-wavelength resonance mode of the trial-produced piezoelectric transformer, the piezoelectric transformer characteristic was measured at an input of 70 Vrms and a load resistance of 10 Ω while supporting a position ¼ from the end face in the length direction of the rectangular plate 41. The results are shown in Table 2.

[0024]

[Table 2]

The same evaluation was performed on the conventional structure in which the linear internal electrode group of the input section is exposed every other layer in the lengthwise direction of the rectangular plate 41. The results are also shown in Table 2. According to this, in the piezoelectric transformer according to the present invention, the capacitance ratio on the input side is 7 in comparison with the conventional structure in which the linear internal electrode group of the input section is exposed every other layer in the length direction of the rectangular plate 41. 5, it is shown that this is improved in the case of the piezoelectric transformer of the present invention by the external electrodes (the input side electrodes 42, 43,
Since the piezoelectrically inactive portion near the output side surface electrode 45) does not exist on the input side, it is considered that the vibrator characteristics are improved.

Further, the bending strength of the piezoelectric transformer according to the present invention has no inactive portion, which is a starting point of destruction of the piezoelectric transformer during polarization or driving, at the input portion, so that the linear internal electrode groups are alternately exposed. It can be seen that the structure is improved over the conventional structure. In Example 3, the linear internal electrodes 44 exposed on the two side surfaces are arranged only in the input section and the output section has the conventional structure, but it can be applied to the output section by a method such as screen printing or sputtering.
In that case, needless to say, the strength and the characteristics of the vibrator can be further improved.

[Embodiment 4] Referring again to FIG. 1, an outline of a vibrator structure according to claim 4 (embodiment 4) of the present invention will be described. Dimension is 32m long
m, width 10 mm, and thickness 6 mm. The linear internal electrodes 14 and 16 made of a silver-palladium alloy are provided in a region of about half of the rectangular plate which is the input portion, with a line width of 100 μm and a length of 9 m.
8 are arranged with a pitch of 2 mm and a pitch of 2 mm, and every other one is alternately exposed on the side surface. Rectangular plate remaining approximately likewise the half area of silver which is the output unit - line width 100 micron linear internal electrodes 15, 17 using a palladium alloy, length 9 mm, arranged 30 present at a pitch 500 [mu] m, every single Alternately exposed to the side. This plane pattern is shown in FIG. The arrow in the figure indicates the polarization direction. Further, 50 layers of this plane pattern are laminated in the thickness direction at intervals of 120 μm. The external electrode for connection with input-output unit linear <br/> shaped internal electrodes 15, 17 which are stacked on each side are provided. Table 3 shows the optimum load calculated from the resonance frequency of the prototype piezoelectric transformer, the oscillator constants on the input and output sides, and the damping capacitance on the output side. In addition, using the one-wavelength resonance mode of the prototyped piezoelectric transformer, the 1
/ 4 position is supported, input 100Vrms, load resistance 30
The piezoelectric transformer characteristics at Ω were measured. The results are shown in Table 3.

[0028]

[Table 3]

[Fifth Embodiment] With reference to FIG. 4 again, an outline of a vibrator structure according to claim 5 (fifth embodiment) of the present invention will be described. Dimension is 32m long
m, width 10 mm, and thickness 6 mm. A silver-palladium alloy was used for about half the area of the rectangular plate 41 which is the input part.
The linear internal electrode 44 has a line width of 100 μm and a length of 9 mm,
Eight pieces are arranged with a pitch of 2 mm, and all are exposed on two side surfaces. Rectangular plate remaining approximately likewise the half area of silver which is the output unit - linear internal electrode 46 using a palladium alloy,
47 with a line width of 100 microns, a length of 9 mm, and a pitch of 500
30 pieces are arranged with a thickness of μm, and every other one is alternately exposed on the side surface. This plane pattern is shown in FIG. The arrow in the figure indicates the polarization direction. Further, 50 layers of this plane pattern are laminated in the thickness direction at intervals of 120 μm.

Further, although the external electrodes to be connected to the input unit linear internal electrodes 46, 47 which are stacked on each side is provided, the input side selects every one linear internal electrodes Then, the rectangular plate is assembled on the upper surface.
Table 3 also shows the optimum load calculated from the resonant frequency of the prototype piezoelectric transformer, the oscillator constants on the input and output sides, and the damping capacitance on the output side.
Shown in.

In addition, by utilizing the one-wavelength resonance mode of the piezoelectric transformer manufactured as a prototype, the rectangular plate 41 is moved from the end face in the longitudinal direction to 1
/ 4 position is supported, input 100Vrms, load resistance 30
The piezoelectric transformer characteristics at Ω were measured. The results are also shown in Table 3.

According to this, it is shown that the capacitance ratio on the input side is improved from 7 to 5, but in the case of the structure of the present invention, the piezoelectrically inactive portion near the external electrode is It is considered that the oscillator characteristics are improved because it does not exist on the input side. Further, it can be seen that the strength of the inactive portion is improved by eliminating it in the input portion, which is a starting point of a crack that causes destruction of the piezoelectric transformer even when the inactive portion is at the extreme or during driving. This time embodiment linear internal electrodes exposed to the two sides in place only on the input unit, an output unit is the same structure as claimed in claim 1, can be applied to the output portion by a method of screen printing, sputtering or the like Needless to say, in that case, it is possible to further improve the strength and the oscillator characteristics.

[0033]

As described above, according to the present invention, since the structure using the linear internal electrodes can be adopted and the laminating direction can be the thickness direction of the piezoelectric ceramic rectangular plate, the manufacturing cost can be reduced. it can. Furthermore, by removing the inactive portion of the piezoelectric transformer, it is possible to provide a piezoelectric transformer having a structure with high mechanical strength and excellent reliability.

Further, it is possible to provide a piezoelectric transformer having a structure having a high mechanical strength and an efficiency of 90% or more by adopting a structure using a linear internal electrode and arranging the laminating direction in the thickness direction of the piezoelectric ceramic rectangular plate. Become. Further, by pulling out the linear electrodes on the side surfaces of the rectangular plate and collecting them on the side surfaces, the upper and lower surfaces, or both end surfaces, it becomes possible to lead at the node point of vibration (the portion where the amplitude is zero), and the reliability can be improved. .

[Brief description of drawings]

1A is a schematic perspective view of a piezoelectric transformer according to claim 1 (embodiment 1), FIG. 1B is a view showing an internal electrode pattern of the piezoelectric transformer of FIG. 1A, and FIG. It is a deformation | transformation schematic diagram at the time of polarization of the piezoelectric transformer of A).

FIG. 2A is a schematic perspective view of a piezoelectric transformer of claim 2 (embodiment 2), and FIG. 2B is a diagram showing internal electrode patterns of the piezoelectric transformer of FIG.

FIG. 3 is a circuit block diagram of a general electromagnetic AC adapter.

FIG. 4A is a schematic perspective view of a piezoelectric transformer of claim 3 (embodiment 3), and FIG. 4B is a diagram showing internal electrode patterns of the piezoelectric transformer of FIG.

[Explanation of symbols]

11 Piezoelectric Transformer Oscillator Rectangular Plate (Piezoelectric Ceramic Rectangular Plate) 12 Input Side Electrodes 13 Output Side Electrodes 14, 16 Input Linear (Strip) Internal Electrodes 15, 17 Output Linear (Strip) Internal Electrodes 21 Piezoelectric Transformer Oscillator rectangular plate 22 Input side electrode 23 Input side electrode 24 Input side internal electrode 25 Output side electrode 26, 27 Output side internal electrode 31 Common mode choke coil 32 for electromagnetic noise suppression Full-wave rectification circuit 33 Smoothing coil 34 Switching circuit 35 Electromagnetic transformer 36 Rectifying circuit 37 Smoothing circuit 41 Piezoelectric transformer vibrator Rectangular plate 42 Input side electrode 43 Input side electrode 44 Input linear (strip) internal electrode 45 Output side electrode 46, 47 Output line (strip) internal electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 41/107

Claims (5)

(57) [Claims] 1. A piezoelectric transformer utilizing a one-wavelength resonance mode in a length direction of a piezoelectric ceramic rectangular plate, wherein the piezoelectric ceramic rectangular plate has at least one partial region divided into two in the length direction, in one partial region the can in the length direction of linear internal electrodes of the plurality of layers by parallel and stacked linear electrode in the thickness direction in the width direction in the multiple plane orthogonal to the longitudinal direction A piezoelectric transformer having a laminated structure , wherein a plurality of layers of linear internal electrode groups are alternately exposed on both side surfaces of the piezoelectric ceramic rectangular plate every other layer in the length direction. 2. A piezoelectric transformer using a one-wavelength resonance mode in the length direction of a piezoelectric ceramic rectangular plate, wherein at least one of two partial regions divided in the length direction of the piezoelectric ceramic rectangular plate. a region, a linear internal electrodes of layers by parallel and stacked linear electrode in the thickness direction in the width direction in the plane of the multiple orthogonal to the longitudinal direction
And it was laminated in the length direction structure, the piezoelectric transformer linear internal electrode groups of the plurality layers, and wherein the exposed on two sides of the piezoelectric ceramic rectangular plate. 3. A piezoelectric transformer using a one-wavelength resonance mode in a length direction of a piezoelectric ceramic rectangular plate, wherein a length is provided in at least one partial region of the piezoelectric ceramic rectangular plate divided into two in the length direction. product a parallel and linear electrodes in the thickness direction in the width direction in the multiple plane orthogonal to the direction
By stacking multiple layers of linear internal electrodes in the length direction,
It has a structure, linear internal electrode groups of the plurality layers, the pressure
Electrostatic exposed to two sides of the ceramic rectangular plate, further, which is connected by a piezoelectric ceramic rectangular plate plurality of side electrodes parallel to the thickness direction provided on the side surface of the length is parallel to the side electrodes of these thickness direction A piezoelectric transformer characterized in that it is drawn out so that every other pole has the same polarity in the vertical direction, and is connected to the side surface, upper and lower surfaces, or both end surfaces of the piezoelectric ceramic rectangular plate. 4. A piezoelectric transformer using a resonance mode in a length direction of a piezoelectric ceramic rectangular plate, wherein the piezoelectric ceramic rectangular plate orthogonal to the length direction is provided in a partial region of the piezoelectric ceramic rectangular plate in the length direction. comprises a first plurality of linear internal electrodes exposed to one side of the plate, and a second plurality of linear internal electrodes perpendicular to the longitudinal direction exposed to the other side of the piezoelectric ceramic rectangular plate, The first plurality
Said second linear internal electrodes arranged substantially in an intermediate position between the linear internal electrodes, these linear internal electrode is connected to the respective common external electrode on both sides of the piezoelectric ceramic rectangular plate, wherein the remaining approximately half of the length direction of the piezoelectric ceramic rectangular plate, a third plurality of linear internal electrodes perpendicular to the longitudinal direction exposed on one side surface of the piezoelectric ceramic rectangular plate, the lengthwise direction And a fourth plurality of strip-shaped internal electrodes that are exposed to the other side surface of the piezoelectric ceramic rectangular plate, and the first to fourth linear internal electrodes are arranged in the width direction.
It is made by stacking linear electrodes in parallel and in the thickness direction.
2. Each of the linear internal electrodes is connected to a common external electrode on the side surface of the piezoelectric ceramic rectangular plate. 5. A piezoelectric transformer using a resonance mode of a piezoelectric ceramic rectangular plate in a longitudinal direction, wherein the piezoelectric ceramic rectangular plate is substantially orthogonal to the longitudinal direction in a partial region of a half of the longitudinal direction of the piezoelectric ceramic rectangular plate and in the thickness direction. Stack multiple linear electrodes on
It made, further, laminating a first plurality of linear internal electrodes exposed to the two sides of the piezoelectric ceramic rectangular plate in the longitudinal direction
Has a structure, a plurality of linear internal electrodes of said first, said piezoelectric while the side surface or the upper surface of the ceramic rectangular plate is connected to the two external electrodes, the remaining substantially half of the length direction of the piezoelectric ceramic rectangular plate The second part is also formed by stacking a plurality of linear electrodes perpendicular to the length direction and in the thickness direction, and further exposed alternately on the two side faces of the piezoelectric ceramic rectangular plate. by laminating a plurality of linear internal electrodes in the longitudinal direction
The structure, a plurality of linear internal electrodes of the second, the piezoelectric transformer, characterized in that connected to the two external electrodes on the side surface or the upper surface of the piezoelectric ceramic rectangular plate.