JP2000269565A - Piezoelectric transformer and driving method thereof - Google Patents

Abstract

(57) [Summary] [Problem] To provide a driving method of a piezoelectric transformer that can improve the mounting efficiency of the piezoelectric transformer and can more easily perform voltage detection in a driving circuit. SOLUTION: A piezoelectric transformer in which an input electrode and an output electrode are formed on a piezoelectric ceramic body is housed in a case, and an input terminal and an output terminal provided in the case and an input electrode and an output provided on the piezoelectric ceramic body are provided. The piezoelectric transformer mounted on the input terminal and the output terminal of the case is connected to each of the electrodes, and the case faces the output voltage electrode portion that is electrically connected to the output electrode of the piezoelectric ceramic body. A capacitance forming electrode for forming a capacitance is formed, and the capacitance is used as an output voltage detecting capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric transformer used in a circuit for generating a high voltage, such as a driving circuit for a fluorescent tube used for a backlight of a liquid crystal display, and a driving method thereof.

[0002]

2. Description of the Related Art Various configurations have been proposed for this piezoelectric transformer. For example, there is a piezoelectric transformer shown in FIG. This piezoelectric transformer is a λ / 2 mode center drive type laminated piezoelectric transformer. This piezoelectric transformer 1
For example, using a piezoelectric ceramic material of lead zirconate titanate (PZT), this slurry is formed into a sheet shape by a doctor blade, and the sheets are laminated and pressed.
It is formed by integrally firing. Before the lamination, the internal electrodes 2, 3 serving as input electrodes are provided at the center of each sheet.
Is formed by screen printing. Each internal electrode 2,
3 are formed so as to face different side surfaces, respectively, and are connected to the input electrodes 4 and 5 on the side surfaces, respectively. As a result, an alternately opposed electrode structure is formed inside the stack.

Each of the internal electrodes 2 and 3 serving as input electrodes is
The connection electrodes 4 and 5 formed on the side face are connected every other layer. The connection electrodes 4 and 5 have a role of connecting the internal electrodes and connecting the outside and the input electrodes. Output electrodes 6 and 7 are formed on both end surfaces of the piezoelectric transformer element 1 having the laminated structure.

In the piezoelectric transformer element 1, a portion on which input electrodes (internal electrodes) 2 and 3 are formed is used as a driving portion. In this driving portion, a polarization process is performed in a thickness direction as indicated by an arrow in the drawing. I have. On the other hand, both sides of the drive section become power generation sections and are polarized in the longitudinal direction as indicated by arrows in the figure.
In the structure shown in FIG. 4, no electrodes are provided on the upper and lower surfaces of the drive unit, but electrodes may be provided on the upper and lower surfaces and connected to the input electrodes 4 and 5, respectively.

FIG. 5 shows an example of a driving circuit for a fluorescent tube using this piezoelectric transformer. This circuit includes a piezoelectric transformer 20
Are connected to the discharge tube 31. The input voltage from the drive circuit 30 is connected to the input electrode 21 of the piezoelectric transformer 20, and the other input electrode 22 of the piezoelectric transformer 20 is connected to the common terminal 304. The other end of the discharge tube 31 is connected to the current detection resistor 32, is connected to the common terminal 304, and is connected to the current detection terminal 302 before the resistor 32. The output of the piezoelectric transformer 20 includes voltage detection resistors 41, 42, 4
3, 44, 45, and 33 are connected to the common terminal 304. The voltage detection resistors 41, 42, 43, and 4
4 and 45 are connected to the voltage detection terminal 303.

[0006]

Since the output electrode of this piezoelectric transformer has a high voltage, an insulation measure corresponding to the high voltage is required near this terminal. In the case of the conventional piezoelectric transformer 1 described above, output electrodes 6 and 7 are formed at both ends. For this reason, when mounting the piezoelectric transformer, a high voltage countermeasure is taken at both ends of the piezoelectric transformer, so that there is a problem that mounting efficiency is not good. This hinders, for example, high-density mounting on a printed circuit board.

In a drive circuit for a discharge tube using this piezoelectric transformer, it is common practice to detect the output of the piezoelectric transformer and feed it back to the drive circuit.
In order to perform this output voltage detection, for example, five 2 MΩ resistors (resistances 41, 42, 43, 44, and 45) are connected in series and detected as 10 MΩ. This means that at an output voltage of 1 kV, the current flowing through 10 MΩ is 0.1 mA.

In view of the above, the present invention provides a piezoelectric transformer capable of improving the mounting efficiency of the piezoelectric transformer, and furthermore, a drive of the piezoelectric transformer which can more easily detect a voltage in a drive circuit. The aim is to provide a method.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a piezoelectric transformer having an input electrode and an output electrode formed on a piezoelectric ceramic body is housed in a case, and an input terminal, an output terminal and the piezoelectric ceramic provided in the case are provided. An input electrode and an output electrode provided on the body are connected to each other, and the input terminal and the output terminal of the case are mounted on a piezoelectric transformer, wherein the case has an output conducting to an output electrode of the piezoelectric ceramic body. A piezoelectric transformer is characterized in that a capacitance forming electrode for forming a desired capacitance is formed facing a voltage electrode portion, and an output terminal of the capacitance is formed.

Further, according to the present invention, a piezoelectric transformer in which an input electrode and an output electrode are formed on a piezoelectric ceramic body is housed in a case, and an input terminal, an output terminal provided in the case and the piezoelectric ceramic body are provided on the case. An input electrode and an output electrode are connected to each other, and in the piezoelectric transformer mounted on the input terminal and the output terminal of the case, the case includes at least two output electrodes provided on the piezoelectric ceramic body. A piezoelectric transformer comprising: a conducting electrode for conducting electricity; and a facing electrode, a capacitance forming electrode for obtaining a desired capacitance, and an output terminal of the capacitance. . In addition, as the piezoelectric transformer, a central drive type piezoelectric transformer in which an input electrode is formed so as to face the center and output electrodes are formed separately at both ends is used.

The present invention also provides a capacitor by providing an electrode corresponding to an output voltage electrode of the piezoelectric transformer on a mounting case of the piezoelectric transformer, and using the capacitor as a capacitor for detecting an output voltage. A driving method for a piezoelectric transformer, wherein feedback control is performed via the capacitor.

Further, according to the present invention, a piezoelectric transformer in which an input electrode and an output electrode are formed on a piezoelectric ceramic body is housed in a case, and the input and output terminals provided in the case and the piezoelectric ceramic body are provided on the case. An input electrode and an output electrode are connected to each other, and in the piezoelectric transformer mounted on the input terminal and the output terminal of the case, the case includes at least two output electrodes provided on the piezoelectric ceramic body. A conducting electrode for conducting electricity is provided, and a capacitance forming electrode for obtaining a desired capacitance is provided facing the conducting electrode. The capacitance is used as a capacitor for detecting an output voltage, and feedback control is performed via the capacitor. And a driving method of the piezoelectric transformer.

According to the present invention, there is provided a driving circuit for a piezoelectric transformer, wherein an input electrode is formed so as to face a central portion, and an output electrode is formed separately at both ends. Can be.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a case where a plurality of piezoelectric transformers are housed and mounted by providing electrodes for conducting a plurality of output electrodes provided on the piezoelectric transformer.
A single high voltage output terminal of the piezoelectric transformer can be provided. This eliminates the need to perform high-voltage countermeasures at two locations as in the conventional case, thereby increasing countermeasure efficiency and achieving high-density mounting.

Further, according to the present invention, a piezoelectric transformer is housed,
In the mounting case, an electrode for obtaining a desired capacitance is provided opposite to the electrode at which the output voltage of the piezoelectric transformer is generated, and the capacitance is used as a capacitor for detecting the output voltage of the piezoelectric transformer. It is not necessary to connect five resistors in series, and it is also possible to eliminate the need to connect a capacitor.

The capacitance can be formed efficiently by making the electrode for the capacitor for detecting the output voltage formed in this case, for example, a structure in which it is opposed to a plurality of conducting electrodes for the output electrode formed in the case.

The present invention will be described below with reference to the drawings. First, a conceptual diagram of a piezoelectric transformer according to an embodiment of the present invention is shown in FIG. 1, and a perspective view of this piezoelectric transformer element portion is shown in FIG. The piezoelectric transformer element 10 of this embodiment has a structure shown in FIG. It is formed in a laminated structure such that the input electrode faces the center. Then, they are alternately connected to the input electrode terminals 16 and 17. Output electrodes are formed at both ends of each layer to be laminated.
8 and 19 are connected. The polarization state inside the piezoelectric transformer element is as shown by an arrow in the figure, and this point is the same as that described in the conventional example.

The piezoelectric transformer element 10 is housed in a case 50. The case 50 has metal terminals 51 and 52 connected to the input electrode terminals 16 and 17 of the piezoelectric transformer element 10, and is formed on the case 50 as input terminals 11 and 12, respectively. In addition, metal terminals 53 and 54 connected to the output electrode terminals 18 and 19 of the piezoelectric transformer element 10 are provided.
5, and is connected to the metal terminal 53, and is connected to the output terminal 13. Then, an electrode 15 facing the conductive electrode 55 is formed, and the capacitor terminal 14 is formed. These terminals 11, 12, 13, and 14 are formed in a state in which they can be surface-mounted. Also, metal terminals 51, 52, 5
The portions connected to the electrodes of the piezoelectric transformer elements 3 and 54 have a springy structure. This case 5
Although 0 is only a conceptual drawing, it goes without saying that a case for achieving this can be appropriately designed.

According to this embodiment, the output terminal 13 is 1
There are only one location, and high-voltage countermeasures can be taken at one location on the mounting board, and high-density mounting is possible. To explain this further, for example, when the piezoelectric transformer element 10 shown in FIG. 2 is used and a case having a conventional terminal structure is used, the structure shown in FIG. 6 is obtained. According to this, the output terminals are 13 and 6
Therefore, it is necessary to take measures against high voltage at two places. In addition, a connection line between the output terminals 13 and 61 must be provided on the mounting board, and not only at the terminal part but also at the connection line. High pressure measures are required. As described above, according to the present invention, it is understood that the mounting efficiency can be improved and excellent effects can be expected.

In the above-described embodiment, the electrode 15 facing the conductive electrode for the output voltage is provided and the terminal 14 is provided. However, this capacitance can be expected to function as a capacitor for detecting the output voltage of the piezoelectric transformer. In a driving circuit for a piezoelectric transformer, the output voltage of the piezoelectric transformer can be detected and fed back to be used as a capacitor for detecting an output voltage of a driving circuit for controlling the output voltage.

FIG. 3 shows a circuit showing a driving method according to an embodiment of the present invention. 3 uses the piezoelectric transformer of the above-described embodiment. In this driving method, the driving voltage output 301 from the driving circuit 30 is connected to the input terminal 11 of the piezoelectric transformer element 10. The other input terminal 12 of the piezoelectric transformer element is connected to the common terminal 304. The output terminal 13 of the piezoelectric transformer element 10
It is connected to the discharge tube 31 and lights up. The discharge tube 31
Are connected to the current detection resistor 32 and to the common terminal 304. Further, the current detection resistor 32 is connected to the current detection terminal 302 of the drive circuit 30 at a previous stage. The output voltage detecting capacitor 34 provided in the case 50 of the piezoelectric transformer 10 is connected to the output voltage detecting terminal 303 and is connected to the common terminal 3 via the voltage detecting resistor 33.
04.

According to this driving method, it is not necessary to use a conventional five resistors connected in series for voltage detection, and a capacitor for voltage detection is formed in the case of the piezoelectric transformer element. No circuit elements are required.
For this reason, in addition to having one output terminal of the piezoelectric transformer, there is no need to newly provide a capacitor for voltage detection, and the number of elements is reduced, high-voltage countermeasures are limited, and high-density mounting is possible.

As the capacitor for detecting the voltage, C
Calculated from = 1 / (2πfX), X = 10 MΩ, and f = 60 kHz, the value is 0.265 pF. If the capacitance is set to this level, the detection resistor can be replaced. With such a capacitance value, it is possible to construct a piezoelectric transformer case as described above.

[0024]

According to the present invention, the output terminal of the piezoelectric transformer formed in the case is provided at one point, and a capacitor which can be used for detecting the output voltage of the piezoelectric transformer is formed in the case. It is possible to improve the mounting efficiency of the piezoelectric transformer and to obtain a driving method of the piezoelectric transformer that can more easily perform voltage detection in the drive circuit.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of one embodiment according to the present invention.

FIG. 2 is a perspective view of a piezoelectric transformer element according to one embodiment of the present invention.

FIG. 3 is a drive circuit diagram of one embodiment according to the present invention.

FIG. 4 is a perspective view of a conventional piezoelectric transformer element.

FIG. 5 is a drive circuit diagram of a conventional example.

FIG. 6 is a conceptual diagram of a conventional piezoelectric transformer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Piezoelectric transformer element 11, 12 Input terminal 13 Output terminal 14 Capacitor terminal 15 Capacitor forming electrode 16, 17 Input electrode terminal 18, 19 Output electrode terminal 30 Drive circuit 301 Drive terminal 302 Current detection terminal 303 Voltage detection Terminal 304 Common terminal 31 Discharge tube 32 Current detection resistor 33 Voltage detection resistor 34 Voltage detection capacitor 50 Case 51, 52, 53, 54 Metal terminal

Claims (5)

[Claims] A piezoelectric transformer having an input electrode and an output electrode formed on a piezoelectric ceramic body is housed in a case, and an input terminal and an output terminal provided on the case and an input electrode provided on the piezoelectric ceramic body are provided. Output electrodes are connected to each other, and the input terminal of the case, the piezoelectric transformer mounted at the output terminal, in the case, facing the output voltage electrode portion conducting to the output electrode of the piezoelectric ceramic body, A piezoelectric transformer, comprising: a capacitor forming electrode for forming a desired capacitor; and an output terminal of the capacitor. 2. A piezoelectric transformer having an input electrode and an output electrode formed on a piezoelectric ceramic body is housed in a case, and an input terminal and an output terminal provided on the case and an input electrode provided on the piezoelectric ceramic body are provided. An output electrode connected to the input terminal and an output terminal of the case, wherein the case is connected to at least two output electrodes provided on the piezoelectric ceramic body. A piezoelectric transformer, comprising: an electrode; a capacitance forming electrode for obtaining a desired capacitance; and an output terminal of the capacitance; 3. The piezoelectric ceramic body, wherein an input electrode is formed so as to face a center portion, and the output electrode is a center drive type piezoelectric transformer formed separately at both ends. The piezoelectric transformer according to claim 2. 4. A capacitor is formed in a mounting case of a piezoelectric transformer by providing an electrode corresponding to an output voltage electrode of the piezoelectric transformer, and the capacitor is used as a capacitor for detecting an output voltage. A piezoelectric transformer driving method, wherein feedback control is performed. 5. A piezoelectric transformer having an input electrode and an output electrode formed on a piezoelectric ceramic body is housed in a case, and an input terminal and an output terminal provided on the case and an input electrode provided on the piezoelectric ceramic body are provided. An output electrode connected to the input terminal and an output terminal of the case, wherein the case is connected to at least two output electrodes provided on the piezoelectric ceramic body. An electrode is provided, and a capacitance forming electrode for obtaining a desired capacitance is provided to face the conductive electrode, and the capacitance is used as a capacitor for detecting an output voltage,
A method for driving a piezoelectric transformer, wherein feedback control is performed via the capacitor.