JP4623399B2 - Piezoelectric transformer drive circuit and piezoelectric transformer mounting board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric transformer driving circuit and a mounting substrate used in a circuit for generating a high voltage, such as a fluorescent tube driving circuit used for a backlight of a liquid crystal display.
[0002]
[Prior art]
As this piezoelectric transformer, various configurations have been proposed. For example, there is a piezoelectric transformer shown in FIG. This piezoelectric transformer is a λ / 2 mode central drive type laminated piezoelectric transformer. The piezoelectric transformer 1 is formed by using, for example, a lead zirconate titanate (PZT) piezoelectric ceramic material, forming a slurry of the slurry into a sheet shape with a doctor blade, laminating, pressing and integrally firing the sheets. It has been done. Prior to the lamination, internal electrodes 2 and 3 serving as input electrodes are formed by screen printing at the center of each sheet. The internal electrodes 2 and 3 are formed so as to face different side surfaces, and are connected to the input electrodes 4 and 5 on the side surfaces, respectively.
Thereby, the electrode structure which opposes alternately is comprised within the lamination | stacking.
[0003]
The internal electrodes 2 and 3 serving as input electrodes are connected to every other layer by connection electrodes 4 and 5 formed on the side surfaces. The connection electrodes 4 and 5 serve to connect the internal electrodes and connect the outside and the input electrodes. Output electrodes 6 and 7 are formed on both end faces of the piezoelectric transformer element 1 having this laminated structure.
[0004]
The piezoelectric transformer element 1 uses a portion where the input electrodes (internal electrodes) 2 and 3 are formed as a drive unit, and the drive unit performs polarization processing in the thickness direction as indicated by arrows in the figure. On the other hand, both sides of the drive unit become power generation units and are polarized in the longitudinal direction as indicated by arrows in the figure. In the structure shown in FIG. 5, electrodes are not 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.
[0005]
An example of a drive circuit of a piezoelectric transformer for lighting the fluorescent tube is shown in FIG. In this circuit, the output electrodes 23 and 24 at both ends of the piezoelectric transformer 20 are connected and connected to a 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, connected to the common terminal 304, and connected to the current detection terminal 302 before the resistor 32. Further, voltage detection resistors 41, 42, 43, 44, 45, 33 are connected to the output of the piezoelectric transformer 20 and are connected to the common terminal 304, and the voltage detection resistors 41, 42, 43, 44, 45 are connected. To the voltage detection terminal 303.
[0006]
[Problems to be solved by the invention]
In the drive circuit of this piezoelectric transformer, in order to detect the overvoltage of the piezoelectric transformer, it is usual to detect the output of the piezoelectric transformer and feed it back to the drive circuit. In addition, for example, two 2 MΩ resistors (resistors 41, 42, 43, 44, 45) are connected in series and detected as 10 MΩ. This means that when the output voltage is 1 kV, the current flowing through 10 MΩ is 0.1 mA. However, in the structure in which five 2 MΩ resistors are connected in series as described above, the number of parts is large and circuit space of the board is also required.
[0007]
In view of the above, an object of the present invention is to provide a piezoelectric transformer drive circuit and a mounting substrate that can more easily perform voltage detection in the piezoelectric transformer drive circuit.
[0008]
[Means for Solving the Problems]
In the present invention, an input electrode to which an input of the piezoelectric transformer is connected and an output electrode to which an output of the piezoelectric transformer is connected are formed on the first surface side of the substrate on which the piezoelectric transformer is mounted . on the side, the output electrode and the counter output voltage detection capacitance formed pattern is formed, to connect the capacitance formed between the output electrode and the output voltage detection capacitance formed pattern on the overvoltage detection circuit It is the drive circuit of the characteristic piezoelectric transformer.
[0009]
In the present invention, an input electrode to which the input of the piezoelectric transformer is connected and an output connection line to which the output of the piezoelectric transformer is connected are formed on the first surface side of the substrate on which the piezoelectric transformer is mounted . An output voltage detection capacitor formation pattern facing the output connection line is formed on the second surface side , and the output voltage detection capacitor formation pattern is connected to an overvoltage detection circuit. is there.
[0010]
Further, in the present invention, the output electrode or the output connection line and the output voltage detection capacitor formation pattern are configured such that one area is formed larger than the other, thereby suppressing capacitance variation due to positional deviation at the time of electrode formation. Ru can be.
[0011]
In the present invention, it is preferable that the piezoelectric transformer has outputs at two locations, and an output electrode corresponding to the output is formed on the substrate .
[0012]
In the present invention, it said substrate epoxy substrate der, the piezoelectric transformer is preferably made is composed of a case housing this piezoelectric transformer device.
[0013]
According to another aspect of the present invention, there is provided a substrate for mounting a piezoelectric transformer, which is used in a driving circuit for the piezoelectric transformer.
[0014]
In the present invention, a multilayer substrate can be used as the substrate, and the output connection line and / or the output voltage detection capacitor formation pattern can be incorporated in the multilayer substrate.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The present invention uses a central drive type piezoelectric transformer having a pair of input electrodes at the center of the piezoelectric transformer and having output electrodes formed at both ends. In this central drive type piezoelectric transformer, output electrodes are formed at both ends, and the output electrodes are conducted and connected to a load such as a fluorescent tube. For this reason, in this invention, the output electrode connected with the output electrode of a piezoelectric transformer is formed in two places on the board | substrate with which a piezoelectric transformer is mounted. And the output connection line which connects the two output electrodes was formed. Further, an output voltage detection capacitor formation pattern capable of obtaining a desired capacitance value is provided opposite to the output connection line, and this capacitance value is connected to an overvoltage detection circuit.
[0016]
This output voltage detection capacitor formation pattern can be designed such that a desired capacitance can be obtained at a distance from the output connection line and an opposing area, and can be provided on the front and back surfaces of the substrate so as to face each other. Further, if the piezoelectric transformer mounting substrate is a multilayer substrate, it can be formed inside the multilayer structure.
[0017]
Further, according to the present invention, an output voltage detection capacitor forming pattern is provided on the mounting board of the piezoelectric transformer, and by detecting the overvoltage based on this capacitance value, for example, five resistors are connected in series as in the prior art. Is unnecessary, and it is also possible to eliminate the need to connect a capacitor.
[0018]
Since this output voltage detection capacitor formation pattern can be produced at the time of substrate manufacture, it is not necessary to add a special element, and the number of steps can be reduced.
[0019]
Hereinafter, the present invention will be described with reference to the drawings.
First, a plan view (a) and a rear view (b) of a part of a mounting board of a piezoelectric transformer according to an embodiment of the present invention are shown in FIG. 1, a conceptual diagram of this piezoelectric transformer is shown in FIG. A perspective view of the portion is shown in FIG. The piezoelectric transformer element 10 of this embodiment is formed in a laminated structure so that the input electrode faces the center part as shown in the structure shown in FIG. The terminals are alternately connected to the input electrode terminals 16 and 17. Further, output electrodes are formed at both ends of each layer to be stacked, and are connected to the output electrode terminals 18 and 19 on the side surfaces. The polarization state inside the piezoelectric transformer element is as indicated by an arrow in the figure, and this point is the same as that described in the conventional example.
[0020]
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 in the case 50 as input terminals 11 and 12, respectively. Further, metal terminals 53 and 54 connected to the output electrode terminals 18 and 19 of the piezoelectric transformer element 10 are provided, and the metal terminals 53 and 54 are formed in the case 50 as the output terminals 13 and 14. Each of the terminals 11, 12, 13, and 14 is formed in a surface mountable state. Moreover, the part connected with the electrode of the piezoelectric transformer element 10 of the metal terminals 51, 52, 53, and 54 has a structure which has a spring property. The case 50 is only a conceptual drawing, but it goes without saying that a case for achieving this case can be designed as appropriate.
[0021]
The substrate 60 on which the piezoelectric transformer 50 is mounted is connected to the input electrodes 61 and 62 to which the input terminals 11 and 12 of the case 50 in which the piezoelectric transformer element 10 is incorporated and the output terminals 13 and 14 are connected. Output electrodes 63 and 64 are formed. The piezoelectric transformer 50 is disposed on the substrate 60, and each terminal and each electrode are soldered and surface-mounted.
[0022]
Between the output electrodes 63 and 64 of the substrate 60, an output connection line 65 is formed to connect the two output electrodes 63 and 64. Thereby, the two output electrodes 63 and 64 are connected and output, and connected to a load such as a fluorescent tube. On the back surface of the substrate 60, an output voltage detecting capacitor forming pattern 66 is formed so as to face the output connection line 65 on the front surface. The output voltage detection capacitor formation pattern 66 is configured to face the output connection line 65 and the output electrode 64 to generate a capacitor. As the substrate 60, an epoxy substrate was used. Moreover, the required part of each pattern is insulated.
[0023]
FIG. 4 shows a circuit illustrating a driving method according to an embodiment of the present invention. The piezoelectric transformer element 10 of FIG. 4 uses the piezoelectric transformer of the above-described embodiment. In this drive circuit, the drive voltage output 301 from the drive control element 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 two output terminals 13 and 14 of the piezoelectric transformer element 10 are electrically connected and connected to the discharge tube 31 so as to be lit. The discharge tube 31 is connected to a current detection resistor 32 and connected to a common terminal 304. Further, the current detection resistor 32 is connected to the current detection terminal 302 of the drive control element 30 before the current detection resistor 32. Further, the capacitance formed by the output voltage detection capacitance forming pattern 66 provided on the substrate 60 functions as the capacitor 34, is connected to the output voltage detection terminal 303, and is connected to the overvoltage detection circuit in the drive control element 30. Is done. Further, it is connected to the common terminal 304 through the voltage detection resistor 33.
[0024]
This drive circuit eliminates the need for a conventional series connection of five resistors for output voltage detection, and does not require an additional circuit element as a voltage detection capacitor. For this reason, it is not necessary to provide a new one, and high-density mounting is possible as the number of elements is reduced.
[0025]
This voltage detection capacitor is 0.265 pF when calculated from C = 1 / (2πfX), X = 10 MΩ, and f = 60 kHz. If configured to obtain a capacitance value of this level, the detection resistor Can be replaced. And if it is a capacity | capacitance value of this grade, it can comprise in the above-mentioned board | substrate structure.
[0026]
In the above-described embodiment, a single epoxy substrate is used as the substrate 60. However, a laminated substrate may be used, and an output connection line or an output voltage detection capacitance forming pattern may be built in the laminated structure.
[0027]
Further, in the above embodiment, a central drive type laminated piezoelectric transformer is used. Although this structure is a preferable structure, a piezoelectric transformer having a single layer structure or a piezoelectric transformer having a driving structure other than the central driving type may be used. Further, when there is one output electrode, the area of the output electrode may be increased, and the structure may be appropriately configured so that a desired capacitance can be formed between the capacitance forming patterns. In addition, one of the opposing electrode patterns can be made larger to suppress the capacity variation due to the positional deviation during manufacturing.
[0028]
【The invention's effect】
According to the present invention, it is possible to improve the mounting efficiency of a piezoelectric transformer by providing a capacitor forming pattern for detecting an output voltage on a substrate on which the piezoelectric transformer is mounted, and to increase the overvoltage in the drive circuit. It is possible to obtain a piezoelectric transformer drive circuit capable of performing detection more simply.
[Brief description of the drawings]
FIG. 1 is a plan view (a) and a back view (b) of a part of a mounting board of a piezoelectric transformer according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram of a piezoelectric transformer according to an embodiment of the present invention.
FIG. 3 is a perspective view of a piezoelectric transformer element according to an embodiment of the present invention.
FIG. 4 is a drive circuit diagram of one embodiment according to the present invention.
FIG. 5 is a perspective view of a conventional piezoelectric transformer element.
FIG. 6 is a drive circuit diagram of a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Piezoelectric transformer elements 11 and 12 Input terminal 13 and 14 Output terminal 16 and 17 Input electrode terminal 18 and 19 Output electrode terminal 30 Drive control element 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 60 Substrate 61, 62 Input electrode 63, 64 Output electrode 65 Output connection line 66 Output voltage detection capacitance forming pattern 67 Connection line

Claims (7)

An input electrode to which the input of the piezoelectric transformer is connected and an output electrode to which the output of the piezoelectric transformer is connected are formed on the first surface side of the substrate on which the piezoelectric transformer is mounted, and on the second surface side of the substrate, said output electrode and the counter output voltage detection capacitance formed pattern is formed, a piezoelectric, characterized by connecting a capacitance formed between the output electrode and the output voltage detection capacitance formed pattern on the overvoltage detection circuit Transformer drive circuit. The first surface side of the substrate on which the piezoelectric transformer is mounted, an input electrode input of the piezoelectric transformer is connected, the output connection line output of the piezoelectric transformer is connected is formed, the second surface side of the substrate A drive circuit for a piezoelectric transformer, wherein an output voltage detection capacitor formation pattern facing the output connection line is formed, and the output voltage detection capacitor formation pattern is connected to an overvoltage detection circuit. It said output electrode or said output connection line and said output voltage detection capacitance forming pattern, the piezoelectric transformer driving circuit according to claim 1 or 2, wherein the one area is larger than the other. 4. The piezoelectric transformer drive circuit according to claim 1, wherein the piezoelectric transformer includes outputs at two locations, and output electrodes corresponding to the outputs are formed on the substrate . What the substrate epoxy substrate der, the piezoelectric transformer is a piezoelectric transformer element and a piezoelectric transformer driving circuit according to any one of claims 1 to 4, characterized by comprising is composed of a case housing this . A substrate for mounting a piezoelectric transformer, wherein the substrate is used in the piezoelectric transformer drive circuit according to claim 1. 7. The substrate for mounting a piezoelectric transformer according to claim 6, wherein the substrate is formed in a multilayer structure, and the output connection line and / or the output voltage detection capacitor formation pattern is built in the multilayer substrate. .

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