JPS639672B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel configuration of a piezoelectric transformer, and aims to reduce the size of the piezoelectric transformer at low frequencies.

A piezoelectric transformer is excited at a resonant frequency, and the highest step-up ratio can be obtained at the resonant frequency. Figure 1 shows a lumped constant equivalent circuit focusing on resonance. In Figure 1, L is the equivalent inductance,
C is the equivalent capacitance, R is the equivalent resonant resistance, C _p 1 is the parallel capacitance of the drive section, C _p 2 is the parallel capacitance of the power generation section,
n is the metamorphic ratio. In order to increase the metamorphic ratio,
Generally, C _p 1≫C _p 2.

These piezoelectric transformers have many features compared to wire-wound transformers, such as (1) being smaller, (2) being nonflammable, and (3) having no electromagnetic induction. is being developed.

FIG. 2 schematically shows a typical structure of a conventional piezoelectric transformer. Explaining FIG. 2, the right half 21 of the piezoelectric ceramic plate is the driving part of the piezoelectric transformer, and electrodes 23 and 24 (hidden in the figure) are provided on both upper and lower surfaces of the piezoelectric transformer. is polarized in the thickness direction. Further, the left half 22 is a power generation section, and an electrode 25 is provided at the right end thereof. The drive part 21 and the power generation part are part of the same piezoelectric ceramic plate, but the power generation part 22 is polarized in the length direction. However, piezoelectric transformers with this conventional structure utilize the basic primary resonance or secondary resonance of the longitudinal vibration mode excited in a piezoelectric ceramic plate, and are not widely used in the tens to hundreds of KHz band. However, for example, a booster circuit for lighting an electroluminescent device requires several kilowatts.
It was considered unsuitable for requests for use in low frequency bands of Hz or lower. The main reason for this was that if the basic configuration of the conventional piezoelectric transformer as illustrated in FIG. 2 remained unchanged, the dimensions would become too large. Furthermore, one of the major drawbacks of such conventional piezoelectric transformers is that their main constituent material is ceramic, which has poor thermal conductivity, and that heat generation becomes significant near the vibration nodes during operation.

The present invention has been made to eliminate the above-mentioned drawbacks, and aims to provide a small piezoelectric transformer in the band of several hundred Hz to several tens of kilohertz.

The basic configuration of the present invention is that two piezoelectric vibrators made of ceramic plates are integrated via a metal plate with good thermal conductivity. For example, it is like the one shown in FIG. 3, in which electrodes 34 and 35 are formed on the upper and lower surfaces of a piezoelectric ceramic plate polarized in the thickness direction, and a transverse effect low impedance oscillator 31 that extends and vibrates in the length direction, and A longitudinal effect high impedance oscillator 32, in which electrodes 36 and 37 are provided at the ends of one side of a piezoelectric ceramic plate polarized in the length direction, and which extends and vibrates in the length direction, is shown in FIG. 3A or FIG. 3B. As shown, they are integrated with each other via a metal plate 33. In this integration, at least the longitudinal effect high impedance vibrator 32 is bonded to the metal plate 33 via the insulating layer 38. The piezoelectric transformer thus obtained is characterized in that the transverse effect low impedance vibrator 31 is used as a driving part, and the longitudinal effect high impedance vibrator 32 is used as a power generating part to utilize a bending vibration mode.
Note that the transverse effect low impedance vibrator 31 may be bonded to the metal plate via an insulating layer, or may be bonded directly to the metal plate. The present invention will be specifically described below using Examples.

[Example 1] FIG. 4 shows an example of a vibrating piezoelectric transformer using the present invention. FIG. 4 shows the bending vibration mode vibration nodes of a metal plate 41 supported by a wire 42, the other end of which is fixed to a metal frame 43, and the metal plate 41
A transverse effect low impedance vibrator 44 shown at 31 in FIG. 3 and a longitudinal effect high impedance vibrator 45 shown at 32 in FIG. 46 in the figure is a glass layer which is an insulator,
Longitudinal effect high impedance resonator 45 and metal plate 41
It is interposed between and insulated. A bending mode piezoelectric transformer is configured in which the transverse effect low impedance vibrator 44 is used as a driving section and the longitudinal effect high impedance vibrator 45 is used as a power generation section. Here metal plate 4
1 is Tohoku Metal's Elinva TE3, and the piezoelectric ceramic plate is Tohoku Metal's NEPEC21 (k ₃₁ = 0.38, k ₃₃
= 0.73ε ^T ₁₁ /ε ₀ = 1960ε ^T ₃₃ /ε ₀ = 1850).

And the resonance frequency ₀ of the piezoelectric transformer is 1.0KHz,
The input voltage was set to 3.0V and the input current was set to 500μA, and the step-up ratio and frequency characteristics were measured. This is shown in Figure 5. It can be seen from FIG. 5 that a boost ratio of 50 or more is easily obtained at ₀ . This step-up ratio of 50 is a value sufficient to turn on electroluminescence. Furthermore, due to the high thermal conductivity of the metal plate, almost no heat generation is observed in the ceramic part at ₀ , and since the metal plate can have a much higher power density than piezoelectric ceramic,
Because phenomena such as fluctuations in resonance frequency and decreases in mechanical quality factor Q _n are inherently less likely to occur,
Despite long-term operation, these adverse phenomena were not observed and good characteristics were exhibited.

[Embodiment 2] FIG. 6 shows an example of a tuning fork type piezoelectric transformer using the present invention. In the figure, 61 is a metal tuning fork, 62
31 is the transverse effect low impedance resonator, and 63 is the longitudinal effect high impedance resonator shown in FIG. 32, which is a piezoelectric transformer bonded to the metal tuning fork 61 through an insulating layer 68. 64,65
is a drive terminal, and 66 and 67 are output terminals. Even if such a tuning fork type piezoelectric transformer is used, Example 1
It is possible to obtain exactly the same characteristics as that of the vibrator type, and it also has the advantage of being easier to support than the vibrating piece type.

[Embodiment 3] FIG. 7 shows an example of the piezoelectric transformer of the present invention using a flat metal tuning fork that vibrates perpendicular to the plane.

In the figure, 71 is a metal flat tuning fork, 72 is a transverse effect low impedance vibrator, 73 is a longitudinal effect high impedance vibrator, 74 and 75 are drive terminals, and 72 is a transverse effect low impedance vibrator.
6 and 77 indicate output terminals. Here, the longitudinal effect high impedance vibrator 73 is bonded to the metal flat plate tuning fork 71 via the insulating layer 78 as in the second embodiment. A flat tuning fork that utilizes such plane-perpendicular vibration has the advantage of being inexpensive because it can be punched out with a press, and the same characteristics as in Example 1 can be obtained.

[Embodiment 4] FIG. 8 shows an example of a piezoelectric transformer of the present invention using an S-shaped metal diaphragm that performs plane-perpendicular vibration. In the figure, 81 is an S-shaped metal bending diaphragm;
82 and 83 are the transverse effect low impedance vibrator and the longitudinal effect high impedance vibrator shown in the previous embodiment, respectively; 88 is an insulating layer; 84 and 85 are drive terminals; and 86 and 87 are output terminals. Further, the arrow in the figure indicates the direction of vibration.

A piezoelectric transformer using such an S-shaped metal diaphragm can achieve a lower frequency than the vibrating piece type or tuning fork type examples, and can obtain the same characteristics as Example 1. .

In the above embodiment, the transverse effect low impedance vibrator used for driving was glued to only one side of the metal plate, but this transverse effect low impedance vibrator was glued to both sides of the metal plate, and one side If the transverse effect low impedance vibrator is wired so that when it is extended, the other transverse effect low impedance vibrator is contracted, a bending vibration mode piezoelectric transformer with even better step-up characteristics can be realized. An example of double-sided drive is
For example, as shown in FIG. 9A, two transverse effect low-impedance oscillators 92 polarized in the direction of the arrow are used as the drive section with a metal plate 91 in between, and they are connected in parallel to drive terminals 94, 95. is taken out, a longitudinal effect high impedance oscillator 93 is used as a power generation section via an insulating layer 98, and an output terminal 96,
It has a structure that takes out 97.

By using such a structure, it is not only possible to further increase the step-up ratio compared to the piezoelectric transformer having the structure shown in Figure 3, but it is also possible to suppress the spurious caused by the longitudinal vibration mode that appears on the higher frequency side than the bending vibration mode. It becomes possible. Furthermore, as shown in FIG. 9B, a longitudinal effect high impedance resonator 93
Using two oscillators, the polarization direction (indicated by the arrow) is determined and the electrical connections are made so that when one longitudinal effect high impedance oscillator extends and the other longitudinal effect high impedance oscillator contracts, the same phase output can be obtained. A vine is also a valid example. When such a structure is used, the output impedance is further reduced than the structure shown in FIG. 9A, and stability against loads is improved. Also in this case, it is natural that spurious noise due to the longitudinal vibration mode can be suppressed.

In addition, in the above embodiment, as a longitudinal effect high impedance vibrator, electrodes 102 and 1 are provided at the end portions of the piezoelectric ceramic plate 101 on the same plane as shown in FIG. 10A.
Although the structure in which electrodes 105 and 1 are provided is shown in FIG.
A similar effect can be obtained with a structure in which 06 is provided. Further, the present invention can also be realized as a three-terminal piezoelectric transformer with a common ground terminal. Figure 10a,
The arrow in b indicates the polarization direction.

As is clear from the above examples, according to the present invention, it is possible to manufacture a piezoelectric transformer that generates less heat in the band of several hundred Hz to several tens of KHz, and has great industrial value.

[Brief explanation of the drawing]

FIG. 1 shows a general equivalent circuit of a piezoelectric transformer. L is equivalent inductance, C is equivalent capacitance, R
is the equivalent resonant resistance, C _p 1 is the parallel capacitance of the drive section, C _p 2
is the parallel capacity of the power generation part, and n is the transformation ratio. Second
The figure shows the structure of a conventional piezoelectric transformer.
Reference numeral 21 is a driving section made of piezoelectric ceramic polarized in the thickness direction, 22 is a power generation section made of piezoelectric ceramic polarized in the length direction, and 23, 24, and 25 are electrodes. FIG. 3 is a diagram showing the basic structure of the piezoelectric transformer of the present invention, in which 31 is a transverse effect low impedance oscillator that is constructed using a piezoelectric ceramic plate polarized in the thickness direction and functions as a driving section, and 32 is a long A longitudinal effect high impedance oscillator that is constructed using a piezoelectric ceramic plate polarized in the horizontal direction and functions as a power generation section.
33 is a metal plate, 34, 35, 36, 37 are electrodes,
38 is an insulating layer. FIG. 4 is Embodiment 1 of the present invention.
41 is a diagram showing a schematic configuration of a piezoelectric transformer of 41.
is a metal plate, 42 is a support wire, 43 is a metal frame, 4
4 is a transverse effect low impedance oscillator constructed using a piezoelectric ceramic plate polarized in the thickness direction, 45 is a longitudinal effect high impedance oscillator constructed using a piezoelectric ceramic plate polarized in the length direction, and 46 is an insulating layer. be. FIG. 5 is a diagram showing the step-up ratio frequency characteristic of the piezoelectric transformer of Example 1. FIG. 6 is a diagram showing a schematic configuration of a piezoelectric transformer according to a second embodiment of the present invention, in which 61 is a metal tuning fork, 62 is a transverse effect low impedance oscillator, 63 is a longitudinal effect high impedance oscillator, and 64 and 65 are Drive terminals, 66 and 67 are output terminals, and 68 is an insulating layer. FIG. 7 is a diagram showing a schematic configuration of a piezoelectric transformer according to a third embodiment of the present invention, in which 71 is a metal flat tuning fork, 72 is a transverse effect low impedance oscillator, 73 is a longitudinal effect high impedance oscillator, 74, 75 is a drive terminal, 76 and 77 are output terminals, and 78 is an insulating layer. FIG. 8 is a diagram showing a schematic configuration of a piezoelectric transformer according to a fourth embodiment of the present invention, in which 81 is an S-shaped metal diaphragm, 82 is a transverse effect low impedance oscillator, 83 is a longitudinal effect high impedance oscillator, 84 , 85 are drive terminals, 86,
87 is an output terminal, 88 is an insulating layer, and arrows in FIG. 8 indicate vibration directions of each part of the S-shaped vibrator. 9A and 9B are diagrams showing a schematic configuration of another embodiment of the piezoelectric transformer of the present invention suppressing the longitudinal vibration mode,
91 is a metal plate, 92 is a transverse effect low impedance resonator, 93 is a longitudinal effect high impedance resonator, 9
4 and 95 are drive terminals, 96 and 97 are output terminals, and arrows in the figure indicate polarization directions. FIG. 10 shows an example of the structure of a longitudinal effect high impedance vibrator that can be used in the present invention. FIG. , and FIG. 3B shows a piezoelectric ceramic plate 104 with electrodes 105 and 106 provided on the end face thereof.
The arrow in the figure indicates the polarization direction.

Claims (1)

[Claims] 1. A transverse effect low-impedance oscillator in which electrodes are arranged on the top and bottom surfaces of a piezoelectric ceramic plate polarized in the thickness direction so that it extends and vibrates in the length direction, and one end of the piezoelectric ceramic plate polarized in the length direction. It consists of a longitudinal effect high impedance oscillator with electrodes disposed in the longitudinal direction so as to extend and vibrate in the longitudinal direction, and a metal plate, the longitudinal effect high impedance oscillator being adhered to the metal plate via an insulating layer, The transverse effect low impedance resonator is bonded to the metal plate either through an insulating layer or directly, the drive terminal is taken out from the transverse effect low impedance resonator, the output terminal is taken out from the longitudinal effect high impedance resonator, and then bent. A piezoelectric transformer characterized by utilizing modes.