JP4066393B2 - Piezoelectric transformer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric transformer using piezoelectric ceramics for boosting or stepping down.
[0002]
[Prior art]
With the widespread use of portable electronic devices such as portable TVs and laptop computers, there is an increasing demand for higher efficiency, smaller size, lower height, reduced electromagnetic noise, and lower power consumption. . Therefore, in place of the electromagnetic induction transformer, mounting of a piezoelectric transformer using the energy of mechanical vibration as a conversion medium is being studied. This is because the piezoelectric transformer has a higher energy density and does not emit electromagnetic noise as compared with the electromagnetic induction transformer.
[0003]
On the other hand, although the piezoelectric transformer has almost no radiation noise, it is a capacitive element with respect to conduction noise, so there is a large coupling capacitance between the input and output, and the impedance between the input and output is extremely low. Low resistance to noise. Therefore, the piezoelectric transformer requires countermeasures more than the conventional electromagnetic induction transformer, particularly for common mode (conduction) noise.
[0004]
As an example, when considering an AC adapter, there is a common mode choke coil for conduction noise countermeasures on the input side, then a full-wave rectifier circuit and a large capacitor in parallel with the DC circuit (pulsation suppression that also serves as a countermeasure for instantaneous disconnection) Smoothing capacitor). Next, there is a switching circuit that converts direct current into alternating current, and the alternating current power converted here enters the electromagnetic induction transformer and is converted into a predetermined alternating voltage. Finally, a switching-type AC adapter rectifies the transformed AC power and outputs a predetermined DC power.
[0005]
[Problems to be solved by the invention]
Conventionally, a transformer (transformer) has a large volume among electronic components used in an AC adapter and has a great influence on conversion efficiency.
[0006]
Even if the electromagnetic induction transformer is replaced with a piezoelectric transformer, the entire adapter cannot be reduced in size or height unless the circuit components, such as a common mode choke, before the transformer are reduced in size and height.
[0007]
And if a piezoelectric transformer with a large coupling capacitance between the input and output is adopted, the resistance to common mode noise deteriorates, resulting in an increase in the size of noise countermeasure components, which means that electronic devices are smaller and lower in profile. The feature cannot be obtained.
[0008]
Therefore, an object of the present invention is to provide a piezoelectric transformer having high resistance (immunity) to conduction noise.
[0009]
[Means for Solving the Problems]
The present invention relates to a piezoelectric transformer using the piezoelectric ceramic, an input for the excitation, between the output of the output power take-out, have a shielding portion for noise suppression, the shield portion is a plate A piezoelectric transformer made of a conductor.
[0011]
The present invention is also a piezoelectric transformer using piezoelectric ceramics, comprising a shield part for noise countermeasure between an input part for excitation and an output part for taking out output power, and the shield part Is the above-described piezoelectric transformer made of an internal conductor.
[0012]
The present invention is the above-described piezoelectric transformer in which the internal conductor is formed by electrically connecting a plurality of parallel linear conductors using through holes.
[0013]
Further, the present invention is the above-described piezoelectric transformer in which the inner conductor is electrically connected to a plurality of parallel linear conductors using a side electrode provided on a side surface of the piezoelectric transformer.
[0014]
The piezoelectric transformer of the present invention suppresses common mode noise that has been conducted directly from the input side to the output side even when used as a transformer, improving immunity, and increasing the size of noise countermeasure components such as common mode chokes. The transformer can be reduced in size without doing so.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a piezoelectric transformer using piezoelectric ceramics, characterized by having a noise countermeasure shield part between an input part for excitation and an output part for taking out output power, The piezoelectric transformer is characterized in that the shield part is made of an internal conductor.
[0016]
Embodiments of the present invention will be described below with reference to the drawings.
[0017]
FIG. 1 shows an external perspective view [FIG. 1 (a)] of the piezoelectric transformer according to the first embodiment of the present invention and an AA cross-sectional view [FIG. 1 (b)] of FIG. 1 (a). FIG.1 (c) is the fragmentary sectional view which expanded the C section of FIG.1 (b).
[0018]
The piezoelectric transformer according to the first embodiment of the present invention is a multilayer Rosen-type piezoelectric transformer for boosting that has been most commonly used as a piezoelectric transformer, and includes an input unit 6 and an output unit 7 of the piezoelectric transformer. A shield plate 1 which is a plate-like conductor is provided as a shield part.
[0019]
In the present embodiment, as shown in FIG. 1, the input part 6 and the output part 7 of the piezoelectric transformer are individually formed and then bonded together via the shield plate 1 to obtain a piezoelectric transformer.
[0020]
On the side surface of the piezoelectric transformer, the shield plate 1 is electrically drawn out by the external electrode 2 and grounded.
[0021]
In addition, an external electrode 4 that connects the internal electrode 3 for input to the outside, an external electrode 5 for output, and an end face electrode 8 are provided. The external electrode 4 is also provided on the opposite side in the figure. The configuration of the internal electrode 3 is the same as that of a conventional laminated Rosen piezoelectric transformer.
[0022]
As shown by the arrow 10 in FIG. 1 (c), the input portion 6 is polarized every other layer in the opposite direction in the thickness direction. Moreover, the polarization of the output part is polarized between the external electrode and the end face electrode [FIG. 1 (b)].
[0023]
FIG. 2 is an explanatory diagram of the piezoelectric transformer according to the second embodiment of the present invention. As shown in FIG. 2, the input internal electrode 3 is printed on the green sheets 13 and 14 made of piezoelectric ceramics using a conductor paste, and the input part on the green sheet 13 is used as the internal conductor for the shield part. The conductor 11 was printed in a line on the boundary line between the output part and the through hole 12 was provided in contact with the internal conductor (the conductor 11 printed in a line). The green sheet 13 and the green sheet 14 have different internal electrode shapes, and the internal electrodes 3 and 3a are vertically symmetrical in the figure.
[0024]
And the laminated body which laminated | stacked several green sheets 13 and 14 alternately by the thickness direction was baked, and the piezoelectric transformer (laminated rosen type) of the 2nd Embodiment of this invention was obtained.
[0025]
As shown in FIG. 2C, the obtained shield portion of the piezoelectric transformer has a pseudo surface formed by electrically connecting parallel conductors 11 through through holes 12. The parallel conductors 11 are used because the conductors 11 do not necessarily have a linear shape.
[0026]
Further, the same effect can be obtained when the linear conductors are electrically connected by the side electrodes provided on the side surfaces of the piezoelectric transformer instead of the through holes.
[0027]
FIG. 3 shows an external perspective view [FIG. 3A] of the piezoelectric transformer according to the third embodiment of the present invention, and an AA sectional view [FIG. 3B] of FIG. 3A. . FIG.3 (c) is the fragmentary sectional view which expanded the C section of FIG.3 (b).
[0028]
The piezoelectric transformer of the present embodiment is an example in which the piezoelectric lateral effect of k31 (vibration mode) is used for both the input unit and the output unit, and a shield plate 21 is provided as a shield unit between the input unit 26 and the output unit 27. It is a thing.
[0029]
In the present embodiment, as shown in FIG. 3, the piezoelectric transformer input section 26 and output section 27 are individually formed, and then both are bonded via the shield plate 21 to form a piezoelectric transformer.
[0030]
On the side surface of the piezoelectric transformer, the shield plate 21 is electrically drawn out by the external electrode 22 and grounded.
[0031]
In addition, an external electrode 24 for connecting the input internal electrode 23 to the outside and an external electrode 25 for connecting the output internal electrode 28 to the outside are provided. The external electrodes 24 and 25 are also provided on the opposite side in the figure. The configuration of the internal electrodes 23 and 28 is the same as that of the conventional piezoelectric transformer using the piezoelectric lateral effect of k31 (vibration mode) in both the input unit and the output unit.
[0032]
As shown by the arrow 10 in FIG. 3C, the polarization of the input section 26 is applied every other layer in the opposite direction in the thickness direction. Similarly, the polarization of the output part is applied in the opposite direction in the thickness direction every other layer [FIG. 3 (b)].
[0033]
Similarly to the second embodiment, an input internal electrode is printed on a green sheet made of piezoelectric ceramics using a conductor paste, and the input part on the green sheet is used as an internal conductor for the shield part. A conductor was printed linearly on the boundary line between the output part and a through hole was formed in contact with the inner conductor (conductor printed in a linear form).
[0034]
Then, a fourth embodiment of the present invention having a shield part made of a pseudo surface by firing a laminated body in which a plurality of green sheets in which the shape of the internal electrode is symmetric is alternately laminated in the thickness direction. A piezoelectric transformer of the form (using the piezoelectric lateral effect of k31) was obtained (not shown).
[0035]
FIG. 4 shows an external perspective view [FIG. 4 (a)] of the piezoelectric transformer according to the fifth embodiment of the present invention, and a BB cross-sectional view [FIG. 4 (b)] of FIG. 4 (a). . FIG. 4C is a partial cross-sectional view in which a portion C in FIG. 4B is enlarged.
[0036]
The piezoelectric transformer of the present embodiment is an example in which the piezoelectric longitudinal effect of k33 (vibration mode) is used for both the input unit and the output unit, and a shield plate 31 is provided as a shield unit between the input unit 36 and the output unit 37. It is a thing.
[0037]
In the present embodiment, as shown in FIG. 4, the piezoelectric transformer input section 36 and the output section 37 are individually formed and then bonded together via the shield plate 31 to form a piezoelectric transformer.
[0038]
On the side surface of the piezoelectric transformer, the shield plate 31 is electrically drawn out by the external electrode 32 and grounded.
[0039]
In addition, an external electrode 34 that connects the input internal electrode 33 to the outside and an external electrode 35 that connects the output internal electrode 38 to the outside are provided. The external electrodes 34 and 35 are also provided on the opposite surface in the drawing. The configuration of the internal electrodes 33 and 38 is the same as that of the conventional piezoelectric transformer using the piezoelectric longitudinal effect of k33 (vibration mode) in both the input part and the output part.
[0040]
As shown by the arrow 10 in FIG. 4 (c), the input portion 36 is polarized in the opposite direction in the length direction every other layer. Similarly, the polarization of the output portion is applied in the opposite direction in the length direction every other layer [FIG. 4 (b)].
[0041]
Similarly to the second embodiment, an input internal electrode is printed on a green sheet made of piezoelectric ceramics using a conductor paste, and the input part on the green sheet is used as an internal conductor for the shield part. A conductor was printed linearly on the boundary line between the output part and a through hole was formed in contact with the inner conductor (conductor printed in a linear form).
[0042]
Then, a piezoelectric transformer (k33) according to the sixth embodiment of the present invention having a shield part made of a pseudo surface by firing a laminate in which a plurality of green sheets obtained as described above are laminated in the thickness direction. (Not shown) was obtained.
[0043]
5A and 5B show a piezoelectric transformer according to a seventh embodiment of the present invention. FIG. 5A is an external perspective view of the piezoelectric transformer, and FIG. 5B is a cross-sectional view taken along line AA in FIG. FIG.5 (c) is the fragmentary sectional view which expanded the C section of FIG.5 (b).
[0044]
The piezoelectric transformer according to the present embodiment is a piezoelectric transformer using a thickness longitudinal effect of kt (vibration mode) in both the input unit and the output unit, and a shield plate that is a shield unit between the input unit 46 and the output unit 47. 41 is provided.
[0045]
In the present embodiment, as shown in FIG. 5, the piezoelectric transformer input section 46 and the output section 47 are individually formed and then bonded together via the shield plate 41 to form a piezoelectric transformer. The shield plate may be formed by printing a conductor paste at the time of forming the laminate. Further, since the shield plate only needs to form a pseudo surface, it may be in the form of a streak, a lattice, or a net.
[0046]
On the side surface of the piezoelectric transformer, the shield plate 41 is electrically drawn out by the external electrode 42 and grounded.
[0047]
Further, an external electrode 44 that connects the input internal electrode 43 to the outside and an external electrode 45 that connects the output internal electrode 48 to the outside are provided. The external electrodes 44 and 45 are also provided on the opposite surface in the figure. The configuration of the internal electrodes 43 and 48 is the same as that of the conventional piezoelectric transformer using the piezoelectric thickness longitudinal effect of kt (vibration mode) in both the input part and the output part.
[0048]
As shown by the arrow 10 in FIG. 5C, the input portion 46 is polarized in the opposite direction in the thickness direction. Similarly, the polarization of the output portion is applied in the opposite direction in the thickness direction every other layer.
[0049]
The input / output waveform of the piezoelectric transformer according to the seventh embodiment obtained as described above and V _g which is an index indicating the conductivity of the common mode noise were measured. As in the case of the piezoelectric transformer, V _g is greatly reduced, and the conductivity of common mode noise is greatly improved.
[0050]
The effects of the present invention will be described specifically with reference to the drawings, taking as an example the piezoelectric transformer of the sixth embodiment of the present invention (the piezoelectric longitudinal effect of k33 is used for both the input unit and the output unit).
[0051]
6A and 6B are diagrams for explaining the effect of the present invention. FIG. 6A shows input / output waveforms of a conventional piezoelectric transformer, FIG. 6B shows input / output waveforms of the piezoelectric transformer of the present invention, and FIG. 6 (c) shows a measurement circuit for V _g , and FIG. 6 (d) shows a measurement result for V _g .
[0052]
As shown in FIGS. 6A and 6B, the input / output waveforms (V _in and V _out ) of the conventional piezoelectric transformer and the input / output waveforms of the piezoelectric transformer of the present invention are hardly changed. In the figure, the vertical axis represents voltage (V) and the horizontal axis represents time (t).
[0053]
As shown in FIG. 6D, V _g (52 in the figure) of the conventional piezoelectric transformer was 80 mV _P-P , whereas V _g (51 in the figure) of the piezoelectric transformer of the present invention is 24 mV _P-P , and the function of conducting common mode noise from the input side to the output side was greatly suppressed. In the figure, the vertical axis represents V _g and the horizontal axis represents time (t).
[0054]
As shown in FIG. 6C, V _g is grounded at one end on the input side via a resistor R _S (51Ω in this case) defined by the standard, and at the same time, one end on the output side is grounded. It is measured as the potential difference before and after R _S. Rout is a load resistance (in this case, 18Ω).
[0055]
The piezoelectric transformer subjected to the above measurement has a size of 32 mm × 10 mm × 6 mm, a rated input of 10 v, a rated output of 2.5 v, and the inner conductor is a green sheet input portion made of a high Qm material having a thickness of 60 μm. A through hole having a diameter of 100 μm was provided on the boundary line between the part to be formed and the part to form the output part, and then a conductive paste using a silver-palladium alloy was printed on the boundary line to a width of 80 μm.
[0056]
Then, 50 green sheets having internal conductors and through holes were stacked, pressed, and baked to form a shield part. The width of the external electrode connected to the shield part was 200 μm. The internal and external electrodes for input / output were formed in the same manner as before.
[0057]
【The invention's effect】
As described above, when the piezoelectric transformer of the present invention is used as a transformer, it is possible to reduce the coupling capacity between the input and output without increasing the size of a noise countermeasure component such as a common mode choke. It became possible to improve immunity. That is, according to the present invention, a piezoelectric transformer having high resistance (immunity) to conduction noise can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram showing a piezoelectric transformer according to a first embodiment of the present invention, FIG. 1 (a) is an external perspective view of the piezoelectric transformer, and FIG. 1 (b) is an AA cross section of FIG. 1 (a). FIG. 1 and FIG. 1C are partial cross-sectional views enlarging a portion C in FIG.
2A and 2B are explanatory diagrams of a piezoelectric transformer according to a second embodiment of the present invention, FIGS. 2A and 2B are explanatory diagrams showing the configuration of a green sheet, and FIG. 2C is an internal conductor; Explanatory drawing of the shield part comprised with a through hole.
3A and 3B are views showing a piezoelectric transformer according to a third embodiment of the present invention, FIG. 3A is an external perspective view of the piezoelectric transformer, and FIG. 3B is an AA cross section of FIG. FIG. 3 and FIG. 3C are partial cross-sectional views enlarging a portion C of FIG.
4A and 4B are views showing a piezoelectric transformer according to a fifth embodiment of the present invention, FIG. 4A is an external perspective view of the piezoelectric transformer, and FIG. 4B is a cross-sectional view taken along line BB in FIG. FIG. 4 and FIG. 4C are partial cross-sectional views enlarging the part C of FIG.
5A and 5B are diagrams showing a piezoelectric transformer according to a seventh embodiment of the present invention, FIG. 5A is an external perspective view of the piezoelectric transformer, and FIG. 5B is a cross-sectional view taken along line AA in FIG. FIG. 5 and FIG. 5C are partial cross-sectional views in which a portion C of FIG. 5B is enlarged.
6A and 6B are diagrams for explaining the effects of the present invention, FIG. 6A is a diagram showing input / output waveforms of a conventional piezoelectric transformer, FIG. 6B is a diagram showing input / output waveforms of the piezoelectric transformer of the present invention, FIG. 6C shows a V _g measurement circuit, and FIG. 6D shows a V _g measurement result.
[Explanation of symbols]
1, 21, 31, 41 Shield plate 2, 22, 32, 42 External electrode 3, 3a, 23, 33, 43 (connected to shield plate) Internal electrode 4, 24, 34, 44 (input) External electrodes 5, 25, 35, 45 (for output) External electrodes 6, 26, 36, 46 Input section 7, 27, 37, 47 Output section 8 End face electrodes 28, 38, 48 (for output) Internal electrode 10 (indicating polarization direction) arrow 11 (linear) conductor 12 through hole 13, 14 green sheet 51 (in the piezoelectric transformer of the present invention) V _g
52 V _g (of conventional piezoelectric transformer)

Claims (4)

It is a piezoelectric transformer using piezoelectric ceramics, and has a shield part for noise countermeasure between an input part for excitation and an output part for taking out output power,
The piezoelectric transformer, wherein the shield part is made of a plate-like conductor. It is a piezoelectric transformer using piezoelectric ceramics, and has a shield part for noise countermeasure between an input part for excitation and an output part for taking out output power,
The piezoelectric transformer, wherein the shield part is made of an internal conductor. 3. The piezoelectric transformer according to claim 2 , wherein the inner conductor is formed by electrically connecting a plurality of parallel linear conductors using through holes. 3. The piezoelectric transformer according to claim 2 , wherein the inner conductor is formed by electrically connecting a plurality of parallel linear conductors using a side electrode provided on a side surface of the piezoelectric transformer.

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