JP3365248B2 - Piezoelectric transformer and power conversion device using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter such as an inverter for a backlight of a liquid crystal display or a DC-DC converter, and a piezoelectric transformer used for the same.

[0002]

2. Description of the Related Art Generally, in a liquid crystal display, since the liquid crystal itself does not emit light, a backlight system in which a discharge tube such as a cold cathode tube is arranged on the back surface or side surface of the liquid crystal display is predominant. In order to drive this discharge tube, an AC high voltage of several hundreds of volts or more is required, depending on the length and diameter of the discharge tube itself. An inverter using a piezoelectric transformer is known as a method for generating this AC high voltage.
It is shown in Japanese Patent No. 4492. The structure of the piezoelectric transformer is extremely simple because it does not require windings, and it is possible to reduce the size, thickness, and cost. The principle and characteristics of this piezoelectric transformer are shown in "Piezoelectric transformer characteristics and its application" in the July 1971 issue of a specialized magazine [Electronic Ceramics] published by Gakudensha.

In 1956, C. A. The Rosen type piezoelectric transformer announced by Rosen is shown in FIG. Figure 1
The structure of this Rosen type piezoelectric transformer will be described with reference to 0, and 2 is, for example, lead zirconate titanate (PZT) system.
This is a plate-shaped piezoelectric ceramic element consisting of a pair of input electrodes 4 and 6 provided by, for example, silver baking on the upper and lower surfaces of the left half of this ceramic element in the figure, and on the right end surface in the same manner. The output electrode 8 is formed. Then, the left half drive section of the ceramic element 2 is polarized in the thickness direction, and the right half power generation section is polarized in the length direction as indicated by arrows.

In the piezoelectric transformer thus formed, when an AC voltage having a frequency substantially the same as the resonance frequency in the longitudinal direction of the ceramic element 2 is applied from the AC voltage source 10 between the input electrodes 4 and 6, the ceramic element 2 will be A strong mechanical vibration is generated in the length direction, and as a result, electric charges are generated by the piezoelectric effect in the power generation section in the right half, and one of the output electrode 8 and the input electrode,
For example, the output voltage Vo is generated between the input electrode 6 and the input electrode 6. As shown in FIG. 11 (A), the vibration modes of this ceramic element 2 are a half-wavelength mode (λ / 2 mode in the figure) that resonates at a half-wavelength in the length direction, and a vibration mode as shown in FIG. 11 (B). 2 of all wavelength modes (λ mode in the figure) that resonate at one wavelength
There is one. Since the external dimensions of this piezoelectric transformer are inversely proportional to the frequency, it is necessary to raise the drive frequency as high as possible in order to reduce the size.

However, if the frequency is too high, in the backlight of the liquid crystal display, a high frequency current will flow to the peripheral portion via stray capacitance from the discharge tube or wiring, and a sufficient tube current will not flow to the discharge tube. Efficiency decreases. Therefore, it is necessary to reduce the driving frequency of the driving high-frequency voltage as much as possible. In such a liquid crystal display backlight inverter, it is necessary to lower the frequency as much as possible in order to miniaturize the device, and if the length is the same, the resonance frequency of the half-wavelength mode piezoelectric transformer element is the full-wavelength mode. It is advantageous because it becomes half of that. For this reason, the step-up ratio is not as high as that of the full-wavelength mode, but a half-wavelength mode transformer is being studied and used due to a strong demand for downsizing of the device.

An example of a power conversion circuit using this piezoelectric transformer is shown in FIG. 12, and the waveforms of the output voltage Vo and the drive voltage V3 of the piezoelectric transformer 12 of this circuit are shown in FIG. The inductance of the inductance means 14 and the output capacitance of the MOSFET 16 as the switch means, the piezoelectric transformer 1
By the resonance due to the input capacitance of 2, the piezoelectric transformer 12
Since the drive voltage V3 has a half-wave sinusoidal waveform as shown in FIG. 13, the switching loss of the MOSFET 16 is reduced. Reference numeral 18 is a drive / oscillation unit. Since such a half-wave sine wave contains a relatively large amount of second-order harmonics with respect to the fundamental wave, the piezoelectric transformer 12 is mainly driven by two frequency components of the fundamental wave and the second-order harmonic wave. It In this case, if the drive frequency is approximately equal to the half-wavelength mode resonance frequency of the piezoelectric transformer 12, the second harmonic of the drive voltage V3 becomes substantially equal to the full-wavelength mode resonance frequency, and the piezoelectric transformer 12 has two vibration modes. To do. Therefore, the output voltage Vo of the piezoelectric transformer 12 becomes a distorted wave by combining the two vibration modes as shown in FIG. The efficiency of cold-cathode tubes used for backlights of liquid crystal displays decreases when they are driven by waveforms with large distortion, and at the same time, see page 49 of the June 1994 issue of the electronic magazine, Nikkan Kogyo Shimbun. As mentioned, the life is shortened.

[0007]

Therefore, in order to solve the above-mentioned problems, the applicant of the present invention has filed a prior application (Japanese Patent Application No. 7-1
No. 70662), unlike the Rosen type in which one of the lengthwise directions of the piezoelectric ceramic element is used as a drive unit and the other is used as a power generation unit, the central portion in the lengthwise direction of the piezoelectric ceramic element is used as a drive unit and both sides generate power. We proposed a half-wavelength mode central drive type piezoelectric transformer.
According to this central portion drive type piezoelectric transformer, even if the drive voltage is a distorted wave such as a half-wave sine wave, the vibration mode of an even multiple of 1/2 wavelength (λ / 2) is effective. Since they cancel each other out, the vibration of the λ mode, which is the second harmonic, is almost eliminated, and the distortion of the output voltage can be considerably suppressed.

The dimming of the discharge tube is, for example, +5 to +1 from the resonance frequency fr in view of the discharge characteristics of the discharge tube.
This is done by changing the frequency of the drive voltage within the range of 0% to change the amount of light emission. In the central drive type piezoelectric transformer, the frequency at which the power efficiency drops significantly during dimming. A new problem has been found that the bandwidth exists. FIG. 14 is a graph showing this state, and there is a drastic drop in power efficiency between the resonance frequency fr and (1 + 0.1) fr, which is higher by 10% than the resonance frequency fr. The reason why this phenomenon occurs is that the piezoelectric ceramic element has not only vibration modes in the length direction but also vibration modes in the width direction and the thickness direction. Then, it is considered that the above-mentioned phenomenon of reduction in power efficiency occurs.

In order to avoid such a phenomenon, attempts have been made to define the optimum dimension of the piezoelectric ceramic element by the ratio L / W of the length L and the width W of the piezoelectric element. For example, page 164 of [Piezoelectric ceramics and its applications] (edited by
Electronic Materials Manufacturers Association Denpa Shimbun, April 1974), N
IKKEI ELECTRONICICS (1994 1
Pp. 148, issued Jan. 7, and JP-A-8-32134.
Although all of them are related to the Rosen type piezoelectric transformer, these values cannot be applied to the central portion drive type piezoelectric transformer having different vibration modes in the length direction. The present invention has been made to pay attention to the above problems and to solve them effectively. It is an object of the present invention to provide a piezoelectric transformer and a power conversion device using the same that can optimize the size of a piezoelectric body to eliminate the coupling of vibrations in the length direction and the width direction and greatly improve the efficiency. To provide.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is designed so that a piezoelectric body is sandwiched between them.
And a pair of input electrodes are arranged to form a drive section,
Output electrodes are arranged at both ends of the piezoelectric body so that both ends of the drive unit are
In the piezoelectric transformer in which the power generation unit is formed on the side, the ratio L / W between the length L and the width W of the piezoelectric body is 3.1.
0-3.76, 4.10-4.77, 5.10-5.7
It is set within the range of 8, 6.10 to 6.79, 7.11 to 7.79, and an input voltage is applied to the pair of input electrodes.
And the output electrodes are connected to each other
And an output voltage between any one of the input electrodes .

With this structure, the vibration of the piezoelectric body in the length direction and the vibration of the piezoelectric body in the width direction are not coupled, and the output can be efficiently extracted. This piezoelectric body is driven in a half-wavelength mode, and the frequency of the driving voltage is inversely proportional to the length of the piezoelectric body. Therefore, the length of the piezoelectric body can suppress the generation of high-frequency current leaking to the stray capacitance. The frequency is set within a range of about 15 mm to 34 mm in order to hold the frequency within, for example, 110 kHz to 50 kHz. Such a piezoelectric body may be a single plate, but particularly if it is configured as a laminated type in which a very thin piezoelectric sheet and internal electrodes are alternately laminated, a sufficiently large boost can be achieved. Further, the power conversion device having such a piezoelectric transformer can efficiently light, for example, a cold cathode tube or the like.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a piezoelectric transformer and a power conversion device using the same according to the present invention will be described in detail below with reference to the accompanying drawings. 1 is a perspective view showing the operating principle of the piezoelectric transformer according to the present invention, FIG. 2 is a perspective view showing the piezoelectric transformer according to the present invention, and FIG. 3 is a sectional view of the piezoelectric transformer shown in FIG. As shown in the figure, this piezoelectric transformer 20 is
For example, a rectangular parallelepiped piezoelectric body 22 made of a piezoelectric ceramic such as so-called PZT having a composition of Pb (Zr, Ti) O ₃ is provided. 26 is formed as a drive unit 28, and output electrodes 30 and 32 are formed on both end surfaces of the piezoelectric body 22 in the lengthwise direction to form power generation units 34 and 34 on both sides of the drive unit 28.
The piezoelectric body of the drive unit 28 is polarized in the thickness direction as shown by the arrow, and the piezoelectric bodies of the power generation units 34, 34 on both sides are polarized in the direction from the end to the center as shown by the arrow. Is being processed.

Here, the ratio L / W between the length L of the piezoelectric body 22 and this width W is 3.10 to 3.76, 4.10 to 4.7.
7, 5.10-5.78, 6.10-6.79, 7.1
It is set within the range of 1 to 7.79 to prevent a drop in power efficiency in a practical frequency band as described later. That is, in the dimensional ratios other than the above ratio, there is a frequency band in which the power efficiency is significantly reduced. In this case, the thickness T of the piezoelectric body 22 is described as being considerably large in the illustrated example, but actually, it is set to be smaller than the length L by one digit or more. Further, the ratio L1 / L of the length L of the piezoelectric body 22 and the length L1 of the drive unit 28 is
It is preferable to set it within the range of about 0.3 to 0.6. In the piezoelectric transformer 20 thus formed, the driving voltage V1 having a frequency substantially the same as the resonance frequency in the length direction of the piezoelectric body 22 is applied between the input electrodes 24 and 26 from the AC power supply 36. In this case, the substantially central portion of the piezoelectric body 22 in the length direction is supported and fixed, and is vibrated in the half-wavelength (λ / 2) mode. At this time, the drive unit 28 of the piezoelectric body 22 causes strong mechanical vibration in the length direction, and as a result, the power generation units 3 on both sides are generated.
Electric charges are generated in the electrodes 4 and 34 by the piezoelectric effect, and the output electrodes 3
The output voltage Vo is generated between 0 and 32 and one of the input electrodes, for example, the input electrode 26.

Here, as will be described later in detail, within the driving frequency change range, the vibration in the length direction and the vibration in the width direction of the piezoelectric body 22 are not coupled, and a sharp drop in efficiency occurs. Can be prevented. FIG. 2 shows a laminated piezoelectric transformer to which the above-mentioned operation principle is applied, and FIG. 3 shows a sectional view thereof. The same parts as those of the transformer shown in FIG. 1 are designated by the same reference numerals.

The laminated piezoelectric transformer shown in FIGS. 2 and 3 is a laminated structure in which the internal electrodes 36 and 38 are alternately sandwiched between the single plate type piezoelectric bodies 22 as described above and laminated. Input voltage V1 is applied to each thin layer
Is applied, the step-up ratio is increased by about several times as many layers as the single plate type. Here, the pair of input electrodes 2
4, 26 are provided on the side of the drive unit 28 of the piezoelectric body 22,
Each of the vertically adjacent internal electrodes 36, 38 is connected to a different input electrode 24, 26 (see FIG. 3). In the method for manufacturing the laminated piezoelectric transformer, a PZT-based ceramic green sheet, that is, a piezoelectric sheet is manufactured by a doctor blade method, and the internal electrodes 36 and 38 are printed on a part of the green sheet by a screen printing method. Then, the sheets are laminated and pressure-bonded and sintered. After that, cutting and polishing are performed, and the input electrodes 24 and 26 and the output electrodes 30 and 32 are provided by silver baking, the internal electrode 36 of one layer is connected to one input electrode 24, and the internal electrode 3 of the other layer is connected.
8 is connected to the other input electrode 26.

Then, the thickness direction of the drive unit 28 and the power generation unit 3
A polarization process in the lengthwise direction of Nos. 4 and 34 is performed to complete the process. In the half-wavelength mode, the central portion in the length direction of the piezoelectric body has the smallest vibration amplitude. Therefore, by providing the input electrodes 24 and 26 at this position and supporting and fixing the piezoelectric transformer at this central portion, The reliability of the lead line connected to the electrode can be improved. Here, the upper and lower ends of the driving unit are dummy layers because they are not polarized, but electrodes are provided on the upper and lower surfaces of the driving unit to form the input electrodes 24 and 2, respectively.
By connecting with 6, the dummy layer can be eliminated. In this case, the excitation of the drive unit is not hindered by the dummy layer unit, and the entire drive unit vibrates uniformly, so that strong mechanical vibration occurs in the length direction, and the output efficiency is significantly improved.

Here, the respective dimensions of the piezoelectric body 22 are set in the same manner as in the case of FIG. That is, the ratio L / W of the length L to the width W of the piezoelectric body 22 is 3.10 to 3.76, 4.
10-4.77, 5.10-5.78, 6.10-6.
It is set within the range of 79, 7.11 to 7.79 to prevent a sharp drop in power efficiency within the drive frequency change range. In this case, the thickness of one green sheet (piezoelectric material sheet) is very thin, 50 to 200 μm. Therefore, the thickness T of the piezoelectric material 22 after the lamination and sintering also varies depending on the number of laminated layers, but only 0.5 to 2 The length is about 0.0 mm, which is smaller than the length L by one digit or more. Therefore, the piezoelectric body 22
The vibrations in the thickness direction of the slab hardly affect the vibrations in the length direction. The ratio L1 / L of the length L of the piezoelectric body 22 and the length L1 of the drive unit 28 is preferably set to about 0.3 to 0.6.

FIG. 4 is a circuit diagram showing an embodiment of a power conversion device which controls the output of the piezoelectric transformer by varying the drive excitation frequency. The same parts as those shown in FIG. 12 are designated by the same reference numerals. One end of the DC input current 40 is connected to one input electrode 24 of the piezoelectric transformer 20 via the switch means 16 such as MOSFET, and the other end is connected to the other input electrode 26. Piezoelectric transformer 20
Inductance means 14 is connected in parallel to the input electrodes 24, 26 of, and the input electrostatic capacitance of the piezoelectric transformer 20 and the inductance of the inductance means 14 form a resonance circuit. Both output electrodes 30 and 32 of the piezoelectric transformer 20 are connected to one end of, for example, a cold cathode discharge tube 42 as a load, and the other end is connected to a DC input power source 40 via an output current detection unit 43.
Connected to. In this output current detector 43, the output current I
o can be detected, and this output is input to the frequency variable unit 44. The frequency varying section 44 varies the drive frequency based on the detected current (voltage), and controls the switch means 16 via the drive / oscillation means 18 with this output signal. The frequency of the drive signal of the frequency changing unit 44 can be manually changed, and the light emission of the cold cathode discharge tube 42 is adjusted (dimming).

The output of the DC input power supply 40 is turned on by the switch means 16 which receives a signal from the drive / oscillation section 18.
By being off-controlled, a driving voltage V3 of, for example, a half-wave sine wave is generated, and the input electrodes 24, 26 of the piezoelectric transformer 20
Applied to. This drive voltage is a drive frequency corresponding to the half-wavelength mode of the piezoelectric transformer, and is a distorted wave containing many second harmonics, but the output voltage Vo appearing at the output electrodes 30 and 32 is almost distorted. There is no waveform. This is because the piezoelectric transformer 20 has a structure that does not generate vibrations in all wavelength modes, as described above, and therefore the vibrations of the piezoelectric transformer 20 do not occur even if the drive voltage V3 includes a second harmonic corresponding to all wavelength modes. This is because only half-wavelength mode is available.

Further, the frequency varying section 44 controls the frequency of the driving voltage via the driving / oscillating section 18 so that the output current Io thereof becomes constant when the dimming is not carried out. When dimming is performed, the frequency of the drive voltage V3 is slightly shifted in the + direction from the resonance frequency by controlling the operation of the frequency varying unit 44, but at this time, a phenomenon in which the power efficiency sharply drops may occur. Can be prevented. This is because the frequency of the driving voltage for dimming is generally +5 from the resonance frequency as described above.
The change is made within the range of about + 10%, and even if the drive frequency changes within this frequency change range, the length L of the transformer 20 is set so that the vibration in the length direction and the vibration in the width direction do not cause coupling. And the ratio L / W of the width W within a certain range, that is, 3.10 to 3.76, 4.10 to 4.77, 5.10
This is because it is set within the range of 5.78, 6.10 to 6.79, 7.11 to 7.79. Thus the ratio L / W
By defining the above, the phenomenon in which the vibration in the length direction and the vibration in the width direction cancel each other does not occur, so that the power efficiency can be significantly improved.

As a modification of the above power converter, a rectifying / smoothing means 52 including, for example, two rectifying diodes 46 and 48 and a smoothing capacitor 50 may be provided on the output side of the piezoelectric transformer 20 as shown in FIG. . Further, instead of the output current detecting unit 43 that detects the output state, an output voltage detecting unit 54 may be provided and the detected value may be input to the frequency changing unit 44. Incidentally, 56 is a load.

Next, the ratio L of the length L to the width W of the piezoelectric transformer
/ W is 3.10 to 3.76, 4.10 to 4.77, 5.
10-5.78, 6.10-6.79, 7.11-7.
The reason why it is effective to define it within the range of 79 will be explained using data. FIG. 6 is a graph showing the relationship between the drive frequency and the tube current (output current) of the Inseki type inverter with the cold cathode discharge tube as a load. Fd is the drive frequency, and fr is the resonance frequency (maximum output current Io is obtained. Drive frequency), the horizontal axis is represented by the ratio of the two, and the vertical axis is represented by the tube current Io and the maximum tube current Io as Imax. The dimming of the discharge tube can be performed by changing the tube current Io, but as is clear from this graph, for example, in order to change the tube current within the range of 10% to 100%, the drive frequency ratio is 1. It is understood that the change may be made within the range of 00 to 1.05. In the frequency area where the frequency ratio is smaller than 1.00, the current sharply decreases, which is not preferable for dimming.

FIG. 7 is a graph showing the relationship between the size ratio and the frequency ratio of the central drive type piezoelectric transformer (piezoelectric body) according to the present invention. The ratio L between the total length L of the transformer and its width W is L. The frequency range in which the efficiency sharply decreases when / W is variously changed, that is, the frequency range in which the efficiency deteriorates due to the coupled vibration in the length direction and the width direction of the transformer is indicated by the diagonal lines. As is clear from this graph, the frequency ratio fd / f
When r is in the range of 1.00 to 1.05, the ratio L / W at which efficiency deterioration does not occur is 3.10 to 3.76, 4.10 to 4.7.
7, 5.10-5.78, 6.10-6.79, 7.1
It is in the range of 1 to 7.79, and by defining the size of the piezoelectric body in the size ratio within this range, the efficiency of the transformer is not deteriorated and the efficiency can be maintained high. In this way, the portion where the power efficiency deteriorates as shown by the shaded area in FIG. 7 appears periodically, and the length-width ratio of the piezoelectric transformer is set in the portion excluding this region. The dimensional ratio to be set may be appropriately determined in consideration of the application in which the piezoelectric transformer is used, the mounting space, and the like.

In this case, in order to suppress the leakage current caused by the stray capacitance of the circuit as much as possible, the drive frequency is practically 50 kHz to 110 kHz.
The length L of the laminated piezoelectric material corresponding to this frequency is in the range of 15 mm to 34 mm, and the width thereof is based on the value of the length L and the ratio L / W. W will be decided. Here, the boosting state of the piezoelectric transformer of the present invention designed within the above size ratio and the boosting state of the piezoelectric transformer as a comparative example designed outside the above size ratio will be described using graphs.

In FIG. 8A, the length L is 20.4 mm and the width W is
Drive voltage of a 4.60 mm piezoelectric transformer (curve A1)
It is a graph which shows the relationship between and an output voltage (curve B1).
The dimensional ratio L / W at this time is 4.43, which is set within the above dimensional ratio range, and a cold cathode discharge tube is used as the load. The thickness T of the transformer at this time is 80 μm.
It is made 1.2 mm by stacking 15 sheets of m. As is clear from this graph, even if the driving voltage A1 is a half-wave sinusoidal distortion wave, the output voltage is hardly distorted and the efficiency is not sharply reduced. Further, FIG. 8B shows a graph when the piezoelectric transformer shown in FIG. 8A is used and a normal resistance load is used instead of the cold cathode discharge tube as the load. Also in this case, the output voltage B1 was hardly distorted, and the efficiency was not sharply reduced.

On the other hand, in FIG. 9, the length L is 20.4 m.
It is a wave form diagram which shows the output voltage of the piezoelectric transformer whose m and width W are 5.3 mm. The dimensional ratio L / W at this time is 3.85, which is set outside the dimensional ratio range. A cold cathode discharge tube is used as the load. The thickness T of the transformer at this time is 1.2 mm, which is the same as that used in FIG.
As is apparent from the waveform diagram, it is found that the waveform of the output voltage is considerably distorted, and there is also a sharp decrease in efficiency, which is not preferable.

[0027]

As described above, according to the piezoelectric transformer of the present invention and the power conversion device using the same, the following excellent operational effects can be exhibited. By defining the length-to-width ratio of the half-wavelength mode central drive piezoelectric transformer within a predetermined range, it is possible to prevent the vibration in the length direction and the vibration in the width direction from being coupled. Therefore, when this piezoelectric transformer is used in a power conversion device, it is possible to prevent a sudden drop in power efficiency even if the drive frequency is changed for dimming. In particular, by adopting a laminated transformer as the piezoelectric transformer, it is possible to obtain a high boosting ratio and power efficiency without causing a sharp drop in power efficiency.

[Brief description of drawings]

FIG. 1 is a perspective view showing the operating principle of a piezoelectric transformer according to the present invention.

FIG. 2 is a perspective view showing a piezoelectric transformer according to the present invention.

3 is a cross-sectional view of the piezoelectric transformer shown in FIG.

FIG. 4 is a circuit diagram showing a power conversion device of the present invention using a piezoelectric transformer.

FIG. 5 is a circuit diagram showing a modified example of the power conversion device.

FIG. 6 is a graph showing the relationship between drive frequency and tube current when a cold cathode discharge tube is used as a load.

FIG. 7 is a graph showing the relationship between the dimensional ratio and the frequency ratio of the central drive type piezoelectric transformer of the present invention.

FIG. 8 is a waveform diagram of a drive voltage and an output voltage of the piezoelectric transformer of the present invention.

FIG. 9 is a waveform diagram of the output voltage of the piezoelectric transformer of the comparative example.

FIG. 10 is a perspective view showing the principle of a Rosen type piezoelectric transformer.

FIG. 11 is a diagram showing types of vibration modes.

FIG. 12 is a circuit diagram showing a general power conversion device using a piezoelectric transformer.

FIG. 13 is a waveform diagram of a drive voltage and an output voltage of a conventional Rosen type piezoelectric transformer.

FIG. 14 is a graph showing the relationship between drive efficiency and power efficiency of a conventional center-drive piezoelectric transformer.

[Explanation of symbols]

14 Inductance means 16 switch means (MOSFET) 18 Drive / oscillator 20 Piezoelectric transformer 22 Piezoelectric body 24, 26 Input electrodes 28 Drive 30, 32 output electrodes 34 Power Generation Department 36, 38 internal electrodes 40 DC input power supply 42 Cold cathode discharge tube 44 Frequency variable part 52 Rectification / smoothing means L Piezoelectric length W Piezoelectric width

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-51132 (JP, A) JP-A-7-39144 (JP, A) JP-A-8-69890 (JP, A) JP-A-6- 85343 (JP, A) Japanese Patent Publication 1-20555 (JP, B2) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 41/107 H02M 3/24 H02M 7/48

Claims (7)

(57) [Claims] 1. In a piezoelectric transformer having a piezoelectric body having a drive section formed at the center and power generation sections formed on both sides thereof, the ratio L / W of the length L to the width W of the piezoelectric body is 4 . 10 to
4. A piezoelectric transformer characterized in that it is configured to be set within a range of 4.77. 2. A piezoelectric body is sandwiched at the center thereof.
A pair of input electrodes are arranged to form a driving unit, and
The output electrodes are arranged at both ends of the piezoelectric body so that both sides of the driving unit are
In a piezoelectric transformer that is configured to form a power generation part in
The ratio L / W between the length L and the width W of the piezoelectric body is 3.10.
3.76, 4.10-4.77, 5.10-5.78,
Is set within a range of 6.10～6.79,7.11～7.79, co is applied an input voltage to the pair of input electrodes
The two output electrodes are connected to each other and
A piezoelectric transformer, characterized in that it is configured to obtain an output voltage between any one of the input electrodes . 3. The piezoelectric body is the piezoelectric body in the drive section.
The piezoelectric element is polarized in the thickness direction of the body,
Polarized in the direction from the end of the body to the center
The piezoelectric transformer according to claim 1 or 2, characterized in that
Su. Wherein said piezoelectric body, according to any one of claims 1 to 3, characterized in that it is supported at substantially the center of its length to be driven by the half-wave mode piezoelectric transformer. 5. The piezoelectric body has a length of 15 mm to 34 m.
1 to claim characterized in that it is in the range of m
4. The piezoelectric transformer according to any one of 4 above. 6. The piezoelectric body includes a piezoelectric sheet and the drive.
Is arranged at the position corresponding to the part
The piezoelectric transformer according to any one of claims 1 to 4, characterized in that the internal electrodes are connected alternately laminated alternately. A piezoelectric transformer according to any one of claims 7] claims 1 to 6, and an inductance means constituting the input capacitance and the resonant circuit of the piezoelectric transformer, said piezoelectric transformer to a DC input power source for supplying power Switch means connected between the DC input power source and the inductance means, and drive / oscillation means for generating a drive voltage of a predetermined frequency by switching the switch means. Power converter.