JP2004266222A - Piezoelectric-transformer mounting board, and power-supply apparatus using piezoelectric transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric-transformer mounting board and a power-supply apparatus using a piezoelectric transformer wherein the saving of the space of the board is intended and the sensing of its voltage is affected hardly by the variations of its temperature and humidity. <P>SOLUTION: The piezoelectric-transformer mounting board comprises a board for mounting actually thereon a piezoelectric transformer and a plurality of capacitors provided connectively in series with each other between the output terminal of the piezoelectric transformer and a reference-potential point. Also, the piezoelectric-transformer mounting board has the output-voltage sensing capacitors wherein one of the connection points of the plurality of capacitors is connected with an output-voltage sensing circuit of the piezoelectric transformer, and has metal wirings so patterned on the surface of the board as to provide them connectively among the output terminal of the piezoelectric transformer, the reference-potential point, and the output-voltage sensing capacitors. Further, the output-voltage sensing capacitors are formed by patterning them together with the metal wirings. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power supply device that drives a fluorescent tube used as a backlight of a liquid crystal display using a piezoelectric transformer.
[0002]
[Prior art]
FIG. 4 is a diagram illustrating a configuration of a power supply device including a conventional piezoelectric transformer.
A power supply including the piezoelectric transformer 1 oscillates by setting a drive frequency in an oscillation circuit 2 and supplies the oscillation to a drive circuit 3. When an AC voltage is supplied from the drive circuit 3 to the piezoelectric transformer 1, the piezoelectric transformer 1 is boosted and outputs a high voltage, which is supplied to a load 4 such as a cold cathode tube. The current detection circuit 5 detects a current flowing through the load 4 and feeds it back to the oscillation circuit 3 in order to keep the output power from the piezoelectric transformer 1 applied to the load constant. On the output side of the piezoelectric transformer 1, a voltage detecting resistor 6 and a voltage detecting circuit 7 are provided, and the output voltage of the piezoelectric transformer 1 is fed back to the oscillation circuit 3 (for example, see Patent Document 1).
In addition, there has been one in which a part of the voltage detecting resistor 6 is formed as a capacitor (for example, see Patent Document 2).
[0003]
[Patent Document 1]
JP-A-2000-116157 (paragraph 0014, FIG. 1)
[Patent Document 2]
JP 2000-312038 A (FIG. 4)
[0004]
[Problems to be solved by the invention]
Since the conventional device was configured as described above, the following problems existed. Usually, the cold-cathode tube has an impedance of about 100 KΩ to 200 KΩ, and since it is used at a high frequency, the stray capacitance of the resistance affects the resistance. Therefore, in order to reduce the loss in the voltage detection resistor 6, a resistor of about 1 MΩ to 2 MΩ is used. Need to be connected in series to form a voltage dividing circuit. For this reason, the resistor takes up a large space, and there is a problem that space saving cannot be achieved with the configuration using a plurality of resistors as described above.
[0005]
In some cases, one side of the voltage divider circuit was a capacitor to save space.However, since the effect of temperature and humidity is clearly different between the impedance of the capacitor and the impedance of the resistor, There has been a problem that the detection voltage greatly fluctuates due to the change.
[0006]
The present invention has been made in order to solve the above-described problems, and in particular, to provide a substrate for mounting a piezoelectric transformer, which saves space and hardly causes an influence on a detection voltage due to a change in temperature or humidity. The purpose is to:
[0007]
[Means for Solving the Problems]
The piezoelectric transformer mounting substrate of the present invention includes a substrate on which the piezoelectric transformer is mounted, and a plurality of capacitors connected in series between an output terminal of the piezoelectric transformer and a reference potential point, and a connection point of the plurality of capacitors. One of the output voltage detection capacitors connected to the output voltage detection circuit of the piezoelectric transformer, and the output terminal of the piezoelectric transformer, the reference potential point and the output voltage detection capacitor are patterned on the substrate surface to connect the output voltage detection capacitor. And a metal wiring, wherein the output voltage detecting capacitor is formed by patterning with the metal wiring.
[0008]
Further, the output voltage detecting capacitor is configured such that an electrode surface is orthogonal to the substrate surface, and the metal wiring and the output voltage detecting capacitor are formed on the same surface.
[0009]
Further, the plurality of capacitors constituting the output voltage detecting capacitor are each composed of an electrode pair formed on both surfaces of the substrate.
[0010]
Further, the substrate is composed of a plurality of layers, and the output voltage detecting capacitor has an interlayer electrode formed between the layers.
[0011]
A power supply device using the piezoelectric transformer according to the present invention is mounted on the piezoelectric transformer mounting board according to any one of the above, and generates a piezoelectric transformer for supplying power to a load and an AC voltage for driving the piezoelectric transformer. A drive circuit, an oscillation circuit that sets a drive frequency of the drive circuit, a current detection circuit that detects a current flowing from the piezoelectric transformer to the load, and an output voltage detection circuit that detects an output voltage of the piezoelectric transformer. Prepare.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a piezoelectric transformer mounting substrate and a power supply device using the piezoelectric transformer according to the present invention will be described in detail with reference to the drawings.
The same or equivalent parts as those of the conventional device are denoted by the same reference numerals, and description thereof will be omitted.
[0013]
Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of a power supply device using a piezoelectric transformer according to Embodiment 1 of the present invention.
FIG. 1A is a diagram illustrating a circuit configuration of a power supply device using a piezoelectric transformer according to Embodiment 1 of the present invention, and FIGS. 1B to 1D are diagrams illustrating Embodiment 1 of the present invention. FIG. 3 is a diagram showing an upper surface, a lower surface, and a side surface of a piezoelectric transformer used in the embodiment. In addition, for convenience of explanation, the bottom view of FIG. 1C shows the piezoelectric transformer 1 and the output connector which are mounted on the opposite surface (the surface shown in the top view) of the substrate 11 and cannot be seen originally. It is drawn in a perspective view.
[0014]
As shown in FIGS. 1A and 1C, the substrate for mounting a piezoelectric transformer of the present invention includes an output voltage detecting capacitor 10 for detecting an output voltage of the piezoelectric transformer 1. This output voltage detecting capacitor 10 has a configuration in which a first capacitor 10A provided on the piezoelectric transformer 1 side and a second capacitor 10B provided on the GND side which is a reference potential point are connected in series. The connection point between the first capacitor 10A and the second capacitor 10B is connected to the input side of the voltage detection circuit 7.
Note that the piezoelectric transformer 1 has a transformer element housed in a housing.
[0015]
Here, FIGS. 1A and 1C show a case where the output voltage detecting capacitor 10 is composed of two capacitors. The output voltage detecting capacitor 10 is an output terminal of the piezoelectric transformer 1. 16 comprises a plurality of capacitors connected in series between GND and a reference potential point, and one of the connection points of the plurality of capacitors is connected to the output voltage detection circuit 7 of the piezoelectric transformer 1. The configuration is not limited to the configuration shown in FIG.
[0016]
The output voltage detecting capacitor 10 is formed by patterning a copper film formed on a substrate on which a piezoelectric transformer is to be mounted and by patterning the copper film when wiring is produced.
That is, a copper film (not shown) is formed on the entire surface of the substrate 11 for mounting the piezoelectric transformer 1. When the copper film is etched to form the wiring 12, the output voltage detecting capacitor 10 is simultaneously Form. At this time, the substrate base such as glass epoxy functions as a dielectric of the capacitor.
[0017]
As shown in FIG. 1D, the output voltage detecting capacitor 10 is a capacitor having an electrode surface on a surface of a substrate 11 and orthogonal to the surface. For example, the back surface of a region where the piezoelectric transformer 1 is provided is provided. It may be formed on the side.
[0018]
Specifically, as shown in FIG. 1C, a copper film is formed on the surface opposite to the surface on which the piezoelectric transformer 1 is mounted so that the first capacitor 10A and the second capacitor 10B are connected in series. Perform patterning. In the configuration shown in FIG. 1C, the electrode on the connection point side of the first capacitor 10 </ b> A and the second capacitor 10 </ b> B connected in series is shared, and this shared electrode is connected to the voltage detection circuit 7. Therefore, when patterning the first capacitor 10A and the second capacitor 10B, the wiring 13 connecting the common electrode and the voltage detection circuit 7, the wiring 14 connecting the first capacitor 10A and the output connector, and The wiring 15 for GND of the two capacitors 10B may be patterned together.
The wirings 12, 13, 14, and 15 are metal wirings made of a copper film and patterned on the surface of the substrate 11.
[0019]
Since the output voltage detecting capacitor 10 is formed of a copper film, the electrode area of the capacitor is determined by the thickness of the copper film and the length of the electrode, but by setting the length of the electrode and the distance between the electrodes, A capacitor having a desired impedance can be manufactured.
[0020]
Although the piezoelectric transformer mounting substrate and the power supply device using the piezoelectric transformer according to the first embodiment of the present invention have been described above, the piezoelectric transformer mounting substrate according to the present invention includes an output voltage detecting capacitor 10 and a wiring The power supply device using the piezoelectric transformer of the present invention includes a piezoelectric transformer substrate 11 on which the piezoelectric transformer 1 is mounted, an oscillation circuit 2, a drive circuit 3, a current detection circuit 5, and a voltage detection circuit. 6 is provided.
[0021]
Since the piezoelectric transformer mounting substrate of the present invention includes the output voltage detecting capacitor 10 formed between the piezoelectric transformer 1 and the substrate 11, the piezoelectric transformer mounting substrate according to the present invention has the same structure as the conventional one. A resistor is not required, and the space of the substrate 11 can be saved. In addition, since the power supply device using the piezoelectric transformer of the present invention uses such a piezoelectric transformer mounting substrate, it is possible to save the space of the substrate and to use a power supply device using a piezoelectric transformer with stable operation. Can be provided.
[0022]
Further, since the first capacitor 10A and the second capacitor 10B constituting the output voltage detecting capacitor 10 are both made of the same copper film and a substrate material such as glass epoxy which is a dielectric, the capacitance of the capacitor is determined by the parameter of the capacitance of the capacitor. The temperature coefficient of a certain electrode area, the coefficient of thermal expansion of the distance between electrodes, and the temperature coefficient of the dielectric constant of glass epoxy as a dielectric are basically the same, and even when the temperature and humidity change, the electrode area, the distance between electrodes, and the dielectric constant Since the change in the ratio occurs similarly, the ratio of the two capacitors 10A and 10B does not basically change, so that it is possible to provide a substrate for mounting a piezoelectric transformer that is hardly affected by changes in temperature and humidity.
[0023]
Embodiment 2 FIG.
FIG. 2 is a diagram showing a configuration of a substrate for mounting a piezoelectric transformer according to Embodiment 2 of the present invention.
As shown in FIG. 2, the first capacitor 20A and the second capacitor 20B constituting the output voltage detecting capacitor 20 are both formed by a pair of electrodes formed on both surfaces of the substrate 11, and are connected in series. The electrode 20b on the connection point side of the first capacitor 20A and the second capacitor 20B is shared. As the substrate 21, a substrate having a copper film formed on both surfaces is used. Other configurations are in accordance with the piezoelectric transformer mounting substrate and the power supply device using the piezoelectric transformer according to the first embodiment.
[0024]
The voltage detection circuit 7 is connected to the electrode 20b, and the other electrodes 20a and 20c of the first capacitor 20A and the second capacitor 20B are connected to the piezoelectric transformer 1 and GND, respectively. Since the electrodes 20a and 20c are formed on the surface on which the piezoelectric transformer 1 is mounted, they can be manufactured by patterning in the same manner as in the first embodiment. The electrode 20b is formed on the surface opposite to the surface on which the piezoelectric transformer 1 is mounted, but can be patterned by the same etching method as the electrodes 20a and 20c.
[0025]
FIG. 2 shows only the electrodes 20a, 20b, and 20c constituting the output voltage detection capacitor 20, and includes wiring to the voltage detection circuit 7, wiring to the piezoelectric transformer 1 (to the output connector), and GND. The wiring is not shown, but is patterned on the surface of the substrate 21 as in the first embodiment.
[0026]
As described above, according to the substrate for mounting a piezoelectric transformer according to the second embodiment of the present invention, it is possible to provide a substrate for mounting a piezoelectric transformer that saves space in the substrate 11 and is less affected by changes in temperature and humidity. In addition, since the base material is inserted between the electrodes of the output voltage detecting capacitor 20, no impurities are attached to the electrode surface, and it is hardly affected by humidity, and the operation of the piezoelectric transformer for stable operation is improved. A substrate can be provided.
[0027]
Embodiment 3 FIG.
FIG. 3 is a diagram showing a configuration of a piezoelectric transformer mounting board according to Embodiment 3 of the present invention.
As shown in FIG. 3, the first capacitor 30A and the second capacitor 30B constituting the output voltage detecting capacitor 30 are connected in series, and share the electrode 30b serving as a connection point. The substrate 31 is of a two-layer type, one of which has a copper film formed on both surfaces. Other configurations are in accordance with the piezoelectric transformer mounting substrate and the power supply device using the piezoelectric transformer according to the first embodiment.
[0028]
As shown in FIG. 3, the substrate 31 is of a two-layer type, in which a first layer 31A and a second layer 31B are laminated.
The electrode 30b, which is an interlayer electrode, is formed between the first layer 31A and the second layer 31B, and is formed by etching either the first layer 31A or the second layer 31B on both surfaces.
[0029]
The electrodes 30a and 30c of the first capacitor 30A and the second capacitor 30B are formed by etching as in the first and second embodiments.
FIG. 3 shows only the electrodes 30a, 30b and 30c constituting the output voltage detection capacitor 30, and the wiring to the voltage detection circuit 7, the wiring to the piezoelectric transformer 1 (to the output connector), and the GND wiring are Although not shown, it is patterned together with these electrodes.
FIG. 3 shows a case where the substrate 31 is a two-layer type. However, the substrate 31 may have three or more layers, and the interlayer electrode 30b may be formed between any of the layers. The configuration is not limited to the configuration shown in FIG.
[0030]
As described above, according to the piezoelectric transformer mounting substrate according to the third embodiment of the present invention, it is possible to provide a piezoelectric transformer mounting substrate that is less likely to be affected by changes in temperature and humidity, and saves space in substrate 11. In addition, since the base material is inserted between the electrodes, no impurities are attached to the electrode surface, it is hardly affected by humidity, and a stable operation of the piezoelectric transformer mounting substrate can be provided. it can.
[0031]
【The invention's effect】
The piezoelectric transformer mounting substrate of the present invention includes a substrate on which the piezoelectric transformer is mounted, and a plurality of capacitors connected in series between an output terminal of the piezoelectric transformer and a reference potential point, and a connection point of the plurality of capacitors. One of the output voltage detection capacitors connected to the output voltage detection circuit of the piezoelectric transformer, and the output terminal of the piezoelectric transformer, the reference potential point and the output voltage detection capacitor are patterned on the substrate surface to connect the output voltage detection capacitor. A metal wiring, and the output voltage detecting capacitor is formed by patterning with the metal wiring, so that it can be easily formed and is not easily affected by changes in temperature and humidity. A substrate can be provided.
[0032]
Further, the output voltage detecting capacitor is configured such that an electrode surface is orthogonal to the substrate surface, and the metal wiring and the output voltage detecting capacitor are formed on the same surface, so that the It is possible to provide a piezoelectric transformer mounting substrate that can save space.
[0033]
Further, since the plurality of capacitors constituting the output voltage detecting capacitor are each constituted by an electrode pair formed on both surfaces of the substrate, space can be saved, and the output voltage is affected by changes in temperature and humidity. It is possible to provide a piezoelectric transformer mounting substrate that is difficult to operate and can stably operate as a power supply device.
[0034]
Further, the substrate is composed of a plurality of layers, and the output voltage detecting capacitor has an interlayer electrode formed between the layers, so that space can be saved, and the capacitor is not affected by changes in temperature and humidity. It is possible to provide a piezoelectric transformer mounting substrate that is difficult to operate and can stably operate as a power supply device.
[0035]
A power supply device using the piezoelectric transformer of the present invention includes a piezoelectric transformer mounted on the piezoelectric transformer mounting board according to any one of the above, an oscillation circuit for setting a sweepable frequency, and a frequency set by the oscillation circuit. A driving circuit for supplying an AC voltage for boosting the piezoelectric transformer, a current detecting circuit for detecting a current flowing to a load connected to the piezoelectric transformer, and detecting an output voltage of the piezoelectric transformer. Since the output voltage detecting circuit is provided, the space of the substrate can be saved, and a power supply device using a piezoelectric transformer with stable operation can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a power supply device using a piezoelectric transformer according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of a power supply device using a piezoelectric transformer according to a second embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a power supply device using a piezoelectric transformer according to a third embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a power supply device using a conventional piezoelectric transformer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Piezoelectric transformer, 10, 20, 30 Output voltage detection capacitors, 10A, 20A, 30A First capacitors, 10B, 20B, 30B Second capacitors, 10a, 10b, 10c, 20a, 20b, 20c, 30a, 30b, 30c Electrodes, 11, 21, 31 Substrate, 12, 13, 14, 15 Wiring, 16 output terminals, 31A first layer, 31B second layer.

Claims (5)

A substrate on which the piezoelectric transformer is mounted,
An output voltage comprising a plurality of capacitors connected in series between an output terminal of the piezoelectric transformer and a reference potential point, one of the connection points of the plurality of capacitors being connected to an output voltage detection circuit of the piezoelectric transformer. A detection capacitor;
An output terminal of the piezoelectric transformer, a reference potential point, and a metal wiring patterned on the substrate surface to connect the output voltage detection capacitor, wherein the output voltage detection capacitor is formed by patterning with the metal wiring. A substrate for mounting a piezoelectric transformer. The output voltage detecting capacitor is configured such that an electrode surface is orthogonal to the substrate surface, and the metal wiring and the output voltage detecting capacitor are formed on the same surface. Item 2. The substrate for mounting a piezoelectric transformer according to item 1. 2. The piezoelectric transformer mounting substrate according to claim 1, wherein each of the plurality of capacitors constituting the output voltage detecting capacitor is formed of an electrode pair formed on both surfaces of the substrate. 2. The substrate according to claim 1, wherein the substrate is composed of a plurality of layers, and the output voltage detecting capacitor has an interlayer electrode formed between the layers. A piezoelectric transformer mounted on the piezoelectric transformer mounting board according to any one of claims 1 to 4, and supplying power to a load,
A drive circuit for generating an AC voltage for driving the piezoelectric transformer,
An oscillation circuit for setting a drive frequency of the drive circuit;
A current detection circuit for detecting a current flowing from the piezoelectric transformer to the load,
A power supply device using a piezoelectric transformer, comprising: an output voltage detection circuit for detecting an output voltage of the piezoelectric transformer.

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