JPH10127059A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device that achieves a self-excitation oscillation drive without affecting the output voltage of a piezoelectric transformer and as the same time can improve the reliability in a device with a simple configuration. SOLUTION: An AC voltage is applied to input electrodes 111 and 112 at a drive part 11 of a piezoelectric transformer 1 as an input voltage and an output voltage is outputted from an output electrode 12 at a generation part 12 of the piezoelectric transformer 1, and a charge responding to an output voltage is detected by a feedback electrode 2 that is spaced apart from the front surface and/or the back surface of the generation part 12 of the piezoelectric transformer 1 by a predetermined interval is detected and is fed back to a drive means as a control signal, thus generating a control signal without affecting an output voltage to be outputted to a load side and performing the self-excitation oscillation drive of the piezoelectric transformer 1 and at the same time generating a control signal without mounting an electrode directly to the piezoelectric transformer 1 and hence preventing the vibration of the piezoelectric transformer 1 from being interfered and improving the reliability of a device itself.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter used for OA equipment such as a copying machine and a personal computer, and more particularly to a power converter using a piezoelectric transformer.

[0002]

2. Description of the Related Art In recent years, with the demand for miniaturization of copying machines and the like,
Piezoelectric transformers are being used instead of winding transformers in power converters for generating high voltages.

A piezoelectric transformer is formed on one side in the length direction of a dielectric by subjecting a ferroelectric material such as barium titanate or lead zirconate titanate (PZT) to polarization processing in a thickness direction and a length direction thereof. When an alternating voltage is applied to the driven unit, a high voltage is output from a power generation unit formed on the other side in the length direction of the dielectric due to the electrostriction effect and the piezoelectric effect. For example, JP-A-61-5468
No. 6). In order to drive the piezoelectric transformer, a driving method in which an alternating voltage (or an AC voltage) is applied to the driving unit via a pair of input electrodes provided so as to sandwich the thickness direction (or the polarization direction) of the driving unit. Circuit is required.

FIG. 8 shows an example of a conventional piezoelectric transformer driving circuit. 8, it is assumed that the piezoelectric transformer 1 is polarized in the directions of + and-shown in the figure, and a driving circuit is provided to the input electrode 111 on the positive side (+) of the polarization direction and the input electrode 112 on the negative side (-) of the polarization direction. 300 are connected. In this state, the drive voltage VB is applied to the drive section of the piezoelectric transformer 1 with a positive bias.

The driving circuit 300 has a pull-up n
A push-pull drive circuit comprising a pn-type bipolar transistor 301 and a pnp-type bipolar transistor 302 for pull-down, and an oscillation IC element for performing a switching operation of each of the npn-type or pnp-type transistors 301 and 302 in a complementary manner. For example, TL1
494) An oscillation circuit using 400, in other words, a separately-excited drive circuit configuration is employed.

Next, the operation of the conventional power converter based on the above configuration will be described with reference to FIG. DC input power V
When P is given, the oscillation IC element 400 becomes the variable resistor 4
The control signal of the alternating frequency adjusted at 07 is output to the commonly connected base electrodes of the npn-type and pnp-type transistors 301 and 302. This npn type and pn
Each of the p-type transistors 301 and 302 alternately turns on and off in accordance with the polarity of the control signal, and outputs the drive voltage VB to the piezoelectric transformer 1 by pull-up / pull-down driving of the potential of the input electrode 111 in a complementary manner. This drive voltage VB
, A high output voltage VC is generated from the output electrode 121 provided in the power generation unit of the piezoelectric transformer 1. The generated output voltage VC is converted into a pulsating current by the full-wave rectifying action of the rectifying circuit 108, and is supplied to the load 4 after being smoothed to a direct current via the smoothing capacitor 122.

[0007]

Since the conventional power converter is constructed as described above, the driving circuit 300
The circuit configuration is complicated, and the number of parts increases. That is, as described above, the driving circuit 300
In this case, a push-pull circuit is used as a drive circuit, and an oscillation IC element 400 for operating the transistors 301 and 302 and its peripheral circuit elements are required. There is a problem that an increase in cost cannot be avoided.

The conventional power converter shown in FIG. 9 branches from the output electrode 121 of the piezoelectric transformer 1 and returns to the drive circuit 300 via the waveform shaping section 83, and drives the drive circuit 300 using the feedback control signal. It may be configured to self-excited oscillation of the piezoelectric transformer 1 drives and controls the FETs Q ₃ of the circuit 300. When the control signal is generated by branching from the output electrode 121 and the piezoelectric transformer 1 is self-oscillated by feedback of the control signal, the output voltage VC applied to the load 4 branches from the output electrode 121. Influenced by the control signal, it is impossible to apply all of the output voltage VC to the load 4 and the output voltage VC has a stable waveform.
There is a problem that can not be supplied.

Furthermore, in order to solve the problem of the power converter as shown in FIG. 9, a control electrode for extracting a control signal may be directly connected to the piezoelectric transformer 1.
This directly connected control electrode inhibits the vibration of the piezoelectric transformer 1 and deteriorates the power conversion characteristics, and the connected control electrode drops from the piezoelectric transformer 1 and the like, and the reliability of the power conversion device itself is reduced. Have issues.

Further, in the conventional power converter shown in FIG. 10, the output voltage VC of the piezoelectric transformer 1 is driven and controlled by the self-excited oscillation of the drive circuit 300 via the feedback circuit 8, and the piezoelectric transformer 1 The output voltage VC can be adjusted by the voltage adjustment circuit 6, the voltage control signal generation circuit 7, and the oscillation circuit 8 to increase or decrease the voltage value. However, since the oscillation circuit 8 is required, the circuit configuration is complicated. In addition, the relationship between the AC output value of the piezoelectric transformer 1 and the oscillation frequency of the oscillation circuit 8 changes due to aging or the like, and the reliability of the operation characteristics is reduced, and the cost of the device itself is increased.

In particular, each of the conventional power converters shown in FIGS. 8 to 10 performs separately-excited or self-excited oscillation in a feedback circuit that directly branches a high voltage after power conversion by the piezoelectric transformer 1. Therefore, there is a problem in that this feedback circuit must be configured with components having a high withstand voltage.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and it is possible to perform self-excited oscillation drive without affecting the output voltage of a piezoelectric transformer and improve the reliability of the device with a simple configuration. It is an object of the present invention to provide a power conversion device that can perform the conversion.

[0013]

A power converter according to the present invention is provided with a driving section and a power generation section on a polarized plate-shaped dielectric, and a pair or a plurality of pairs provided on the driving section. In a power converter having a piezoelectric transformer configured to apply an input voltage between input electrodes and extract an output voltage from an output electrode provided in the power generation unit, a power supply is supplied from a power supply according to a feedback signal given to a control electrode. A driving unit that converts the supplied DC voltage into an AC voltage, and applies the converted AC voltage to the dielectric input electrode as the input voltage; and a surface of a power generation unit in the plate-shaped piezoelectric transformer and / or A feedback electrode disposed at a predetermined interval facing the back surface, and a charge accumulated between the feedback electrode and the front and / or back surface of the power generation unit is fed back to the control electrode of the driving means as a feedback signal. In which and a that feedback means.
As described above, in the present invention, the self-excited oscillation driving of the piezoelectric transformer can be performed by generating the feedback signal without affecting the output voltage output to the load side, and the feedback signal can be generated without directly attaching the electrode to the piezoelectric transformer. Since it can be generated, the vibration of the piezoelectric transformer is not hindered, and the reliability of the device itself is improved.

Further, the power converter according to the present invention may include, as necessary, a first support member comprising a plate-like member having a storage recess capable of storing a plate-like piezoelectric transformer; A second member made of a plate-like member for closing the opening of the storage recess;
The first support member and / or the second support member are provided with elastic support protrusions at positions corresponding to the vibrating nodes of the piezoelectric transformer. The return electrode is disposed on the member and / or the second support member at a position corresponding to the power generation section of the piezoelectric transformer, and the output generated in the power generation section by holding the vibrating node of the piezoelectric transformer by the support projection. The voltage is detected by the feedback electrode. As described above, according to the present invention, the piezoelectric transformer is housed in the first and second support members made of plate-like members, and the elastic support protrusions project from the inner surfaces of the first and second support members. Since the vibrating node member of the piezoelectric transformer is sandwiched between the first and second support members, the output voltage generated in the power generation section of the piezoelectric transformer is detected by the feedback electrodes provided on the first and second support members. By interposing a plate-shaped member serving as a first or second supporting member which is an insulator between the dielectric and the electrode, the charge capacity accumulated between the dielectric and the electrode is increased, and a large feedback signal is generated. Can be fed back, and the self-excited oscillation drive can be reliably performed by the feedback signal having a large voltage value without hindering the vibration of the piezoelectric transformer as much as possible.

Further, the power converter according to the present invention is connected to the subsequent stage of the feedback means as needed, and generates and outputs a voltage control signal based on the feedback signal fed back from the feedback means. Generating means, connected to a preceding stage of the driving means, for adjusting a voltage level of a DC voltage supplied from a power supply according to a voltage control signal output from the voltage control signal generating means, And voltage adjusting means for outputting the voltage to the driving means. As described above, in the present invention, the voltage control signal generating means generates the voltage control signal based on the feedback signal of the feedback means, and the voltage adjusting means adjusts the voltage level of the DC voltage supplied from the power supply according to the voltage control signal. Output to the driving means, so that a voltage control signal for adjusting the output voltage of the piezoelectric transformer can be generated by a part of the feedback means without providing an output adjustment circuit including an oscillation device or the like separately. Further, the circuit configuration can be simplified without inhibiting the vibration of the piezoelectric transformer.

In the power converter according to the present invention, if necessary, the voltage control signal generating means adjusts and sets the voltage value of the reference voltage, and the set reference voltage and the feedback signal. A comparison operation unit that generates a voltage control signal by comparing an AC feedback signal output from the means. As described above, in the present invention, the voltage value of the reference voltage set by the voltage setting unit and the AC feedback signal output from the feedback unit are compared by the comparison calculation unit to generate the voltage control signal. Therefore, the ON / OFF of the voltage to be adjusted by the voltage adjusting means based on the setting of the reference voltage in the voltage setting section.
The ratio of the ON state (pulse width) to the OFF period can be controlled, and the output of the piezoelectric transformer having a predetermined step-up ratio can be easily adjusted.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment of the Present Invention) Hereinafter, a power converter according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a block diagram of a power converter according to the present embodiment.

Referring to FIG. 1, the power converter according to the present embodiment has a driving unit 11 and a power generation unit 12 formed by polarizing a flat dielectric, and a pair of input electrodes provided in the driving unit 11. Input voltage VB between 111 and 112
Is applied, the piezoelectric transformer 1 outputs an output voltage VC from an output electrode 121 provided on a flat end surface of the power generation unit 12, and converts a DC voltage VP into an AC voltage according to a feedback signal. And a drive circuit 3 for applying the AC voltage to the input electrodes 111 and 112 of the drive unit 11 as the input voltage VB, and the feedback between the drive circuit 3 and the surface of the power generation unit 12 with a gap 20 at a predetermined interval d. An electrode 2 is provided, and a feedback circuit 8 for feeding back the electric charge accumulated between the feedback electrode 2 and the surface of the power generation unit 12 to the drive circuit 3 as a drive voltage VA of a feedback signal is provided.

Next, the operation of the power converter according to this embodiment based on the above configuration will be described. First, when the DC voltage VP is applied to the drive circuit 3, the drive circuit 3 applies the input voltage VB between a pair of input electrodes 111 and 112 provided in the drive section 11 of the piezoelectric transformer 1 to drive the drive section 3. 11 to generate a voltage in the power generation unit 12 by vibrating,
The generated voltage is output from output electrode 121 to load 4 as output voltage VC. When the output voltage VC is generated, charges are accumulated between the surface of the power generation unit 12 and the feedback electrode 2 disposed so as to form the gap 20 facing the surface of the power generation unit 12, and the accumulated charge amount Is generated, and the drive voltage VA is fed back to the drive circuit 3 via the feedback circuit 8. The drive circuit 3 converts the DC voltage VP input based on the feedback drive voltage VA into an input voltage VB of an AC voltage, and inputs the converted voltage to the piezoelectric transformer 1 again.

As described above, the output voltage VC of the piezoelectric transformer 1
Without affecting the voltage transformer 1, a voltage proportional to the voltage generated in the power generation unit 12 of the piezoelectric transformer 1 is detected, and the detected voltage is fed back to the drive circuit 3 as a drive voltage VA, so that the voltage transformer 1
Can be driven by self-excited oscillation. Further, since the drive voltage VA that is fed back to the drive circuit 3 is detected by the return electrode 8 disposed opposite to the power generation unit 12 of the piezoelectric transformer 1 by a gap 20 with a predetermined interval d, the piezoelectric transformer 1 Does not hinder the piezoelectric characteristics of the device.

(Second Embodiment of the Present Invention) The second embodiment of the present invention
The power converter according to the embodiment will be described with reference to FIGS. FIG. 2 is a circuit configuration diagram of the power converter according to the present embodiment, FIG. 3 is an exploded perspective view of the power converter illustrated in FIG. 2, and FIG. FIG.

In each of the drawings, the power converter according to the present embodiment includes a piezoelectric transformer 1, a feedback circuit 8, and a drive circuit 3 in common with the power converter shown in FIG. And a storage case 5 for storing the piezoelectric transformer 1, and a feedback electrode 2 disposed outside the storage case 5 and connected to the feedback circuit 8. The storage case 5 has a first support member 5a having a concave groove for storing the piezoelectric transformer 1 and a second support member 5 closing an opening of the concave groove of the first support member 5a.
And a supporting member 5b. Each of the first and second support members 5a and 5b is formed of an insulator, and functions as a dielectric between the piezoelectric transformer and the feedback electrode 2.

The first support member 5a is formed of a flexible or elastic plate-like plate made of, for example, a polyester-based resin, and has a suitable center in the width and length directions of the piezoelectric transformer 1. In this configuration, a storage recess 50 large enough to store the piezoelectric transformer 1 is formed with a gap. Semi-cylindrical node support projections 51 and 52 projecting toward the second support member 5b are formed at the bottom of the storage recess 50 so as to be able to abut on the vibration node of the piezoelectric transformer 1 or a position in the vicinity thereof. The input electrodes 111 and 112 are arranged on the semi-cylindrical peripheral surface of each of the node supporting projections. The node supporting protrusions 51 and 52 have appropriate elasticity, and are configured such that the input electrodes 111 and 112 disposed at the distal ends abut on the surface of the piezoelectric transformer 1 by line contact (or point contact). Each of the first and second support members 5a and 5b may have an elastic force generated based on the shape itself, or may have an elastic force generated based on the material itself.

On the inner surface in the width direction of the storage recess 50,
Two pairs of width-direction support projections 53a opposed to each other so as to be able to abut on the vibration node portion of the piezoelectric transformer 1 or a position in the vicinity thereof
53b and 53c, 53d are formed respectively. These width direction support projections 53a, 53b and 53c, 53d
It has a suitable elasticity, and their ends are in contact with the surface of the piezoelectric transformer 1 by line contact (or point contact).

On the inner surface in the longitudinal direction of the storage recess 50,
A pair of longitudinal support protrusions 54a, 54 facing each other
b is formed. These longitudinal support projections 54a, 54b
Has appropriate elasticity, and their ends contact the surface of the piezoelectric transformer 1 by line contact (or point contact).

The second support member 5b is formed of, for example, a polyester resin or the like so as to have flexibility or elasticity. The first support member 5b can be brought into contact with a vibrating node of the piezoelectric transformer 1 or a position in the vicinity thereof. The configuration is such that node supporting protrusions 55 and 56 projecting toward the member 5a are formed. The knot supporting projections 55 and 56 have appropriate elasticity, and are configured such that their tips abut on the surface of the piezoelectric transformer 1 by line contact (or point contact).

The feedback circuit 8 is connected between the feedback electrode 2 disposed on the surface of the power generation unit 12 of the piezoelectric transformer 1 with a gap 20 therebetween and the drive circuit 3, and is connected to the surface of the power generation unit 12 and the drive circuit 3. The configuration is such that an AC control signal generated by the electric charge between the feedback electrodes 2 is shaped into a waveform, and is fed back as a drive voltage VA.

The return electrode 2 is formed by attaching a conductive thin film or attaching a conductive material to the outer surface of the first support member 5a at a position facing the power generation unit 12 of the piezoelectric transformer 1. Configuration.

The end face of the power generation section 12 of the piezoelectric transformer 1 is formed as an output electrode 121, and a lead wire 121a is connected to the output electrode 121 by soldering or the like, and the load 4 is connected via the lead wire 121a. It is a configuration to be connected to. Next, the forming operation and the boosting operation of the power converter according to the present embodiment based on the above configuration will be described.

First, the forming operation of the device of this embodiment is performed in the first
The support member 5a and the second support member 5b are formed by, for example, pressing a film-like or sheet-like plate material. As another processing method, injection molding can be used. The feedback electrode 2 and the input electrodes 111 and 112 are formed at predetermined positions of the first and second support members 5a and 5b thus formed, and the driving circuit 3 and the
A semiconductor chip 57 including a feedback circuit 8 is mounted, and the semiconductor chip 57, the feedback electrode 2, and the input electrode 11 are mounted.
A connection line (not shown) connecting between the I / O terminal 112 and the input / output terminal 58 is formed as a pattern.

The piezoelectric transformer 1 is housed in the housing recess 50 of the first support member 5a, and the second support member 5b is joined to the first support member 5a housing the piezoelectric transformer 1 with an adhesive or a double-sided tape. For example, or integrated by welding by heating or the like.

Next, as to the boosting operation of the device of this embodiment, the first and second support members 5 of the storage case 5 are connected via the drive circuit 3 similarly to the power converter shown in FIG.
The input voltage VB is applied to the piezoelectric transformer 1 via the input electrodes 111 and 112 formed on a and 5b. The drive circuit 3 includes a switching element, for example, an FET (Field Efec).
t Transister; field-effect transistor (hereinafter FET) Q ₃
Is mainly configured of a resistance R ₃ together with the FETs Q _3,
It comprises a coil L ₃ , a capacitor C ₃ , and a Zener diode D _{3. An} input voltage VP is applied to the drain electrode of the FET Q ₃ via the coil L ₃ , and a gate electrode is inputted at the beginning of the startup via a resistor R _3. The voltage VP is applied as a starting voltage. When the turn-on of the FETs Q ₃ in the coil L _3, the energy corresponding to the input voltage VP are stored. The energy stored in the coil L ₃ is superimposed on the input voltage VP at turn-off of the FETs Q _3, an input voltage VB
(+) Is applied to the input electrode 111 of the piezoelectric transformer 1. Note that the capacitor C ₃ and the Zener diode D ₃ connected in parallel to the FET Q ₃ are connected to the piezoelectric transformer 1 and the FET 1 when the input voltage VP becomes equal to or higher than a predetermined value.
It has the effect of protecting the Q _3.

The voltage transformer 1 thus activated
Supplies the output voltage VC to the load from the output electrode 121, and charges proportional to the output voltage VC are accumulated in the gap 20 between the power generation unit 12 of the voltage transformer 1 and the feedback electrode 2. That is, the gap 2 between the surface of the power generation unit 12 and the return electrode 2
At 0, a dielectric composed of an air layer and the storage case 5 is interposed to act as a capacitor.

A voltage corresponding to the electric charge accumulated between the power generation unit 12 and the feedback electrode 2 is generated, and this voltage signal is formed into a waveform by the feedback circuit 8 and then fed back to the drive circuit 3 as a drive voltage VA. Is done. The drive voltage VA to the gate electrode of FETs Q ₃ in the drive circuit 3 is applied actuatable self-oscillation is started.

As described above, the piezoelectric transformer 1 is housed in the housing recess 50 of the housing case 5, and inside the housing, the width direction supporting projections 53a, 53b and 53c, 53 are provided in the width direction.
d, and in the longitudinal direction, between the longitudinal support protrusions 54a, 54b, and further, in the thickness direction, elastically (soft or soft structure) by the nodal support protrusions 51, 52, 55, 56. It is possible to flexibly support the position of the vibration node due to the fluctuation of the vibration frequency or increase the vibration amplitude without the need for the conventional substrate, and the vibration node can be restrained. Vibration can be suppressed and the piezoelectric transformer 1 can be prevented from being broken.

In particular, the feedback electrode 2 for detecting the output voltage VC required for the self-excited oscillation drive is not brought into contact with the piezoelectric transformer 1, and the change in the charge related to the output voltage VC is controlled by the action of the capacitor. Since the voltage is generated, the driving voltage VA can be generated without affecting the output voltage VC, and the piezoelectric transformer 1 is supported by the storage case 5 to support the piezoelectric transformer 1 elastically. Inhibiting the action can be prevented as much as possible.

(Third Embodiment of the Present Invention) FIG. 5 is a circuit diagram of a power converter according to a third embodiment. In the figure, the power converter according to the present embodiment stores the piezoelectric transformer 1 in the storage case 5 similarly to the embodiment device shown in FIG.
21b (corresponding to 2 in FIG. 2) is provided, and the driving circuit 3 is driven based on the driving voltage VA output from the feedback electrodes 21a and 21b to perform self-excited oscillation. The arrangement of 21b and the circuit configuration of the drive circuit 3 are different, and the feedback circuit 8 is configured to feed back the drive voltage VA without performing waveform shaping (see FIG. 2).

The return electrodes 21a and 21b are disposed to face the outer sides of the upper and lower surfaces of the storage case 5, respectively, and the front and back surfaces of the power generation unit 12 of the piezoelectric transformer 1 stored in the storage case 5 are mutually connected. In this configuration, electric charges corresponding to the output voltage VC generated in the power generation unit 12 are respectively stored.

The driving circuit 3 includes a resistor R ₃₁ , a switch S ₃ , a coil L ₃ , and a capacitor C around two Darlington-connected bipolar transistors Q ₃₁ and Q _32.
3 and a resistor R ₃₂ . The two Darlington-connected bipolar transistors Q ₃₁ and Q ₃₂ can greatly amplify and control the drive voltage VA fed back from the feedback circuit 8, eliminating the need for an auxiliary circuit for waveform shaping in the feedback circuit 8. Becomes

(Fourth Embodiment of the Present Invention) FIG. 6 is a block circuit configuration diagram of a power converter according to a fourth embodiment, and FIG. 7 is a detailed circuit configuration diagram of the power converter shown in FIG. . In each of the drawings, the power converter according to the present embodiment converts the DC voltage from the power supply VP to a predetermined AC voltage by the piezoelectric transformer 1, the feedback circuit 8, and the drive circuit 3 in the same manner as in the embodiment shown in FIG. The return electrode 2 is disposed at a distance from the power generation unit 12 of the piezoelectric transformer 1.
The piezoelectric transformer 1 is driven and controlled by self-oscillation based on a feedback signal from the power supply. In addition to this configuration, the voltage level of the DC voltage supplied from the power supply VP is adjusted according to the voltage control signal. A voltage adjusting circuit 6 for outputting the obtained DC voltage to the driving circuit 3 and a voltage control signal connected between the feedback circuit 8 and the voltage adjusting circuit 6 based on a feedback signal fed back from the feedback circuit 8. And a voltage control signal generation circuit 7 for generating the voltage control signal and outputting the voltage control signal to the voltage adjustment circuit 6.

The return electrode 2 includes a first return electrode 22a disposed on one side surface of the power generation unit 12 of the piezoelectric transformer 1 with a gap 20a therebetween, and a first return electrode 22a.
And a second return electrode 22b disposed on the other side of the power generation unit 12 so as to be opposed to the power generation unit 12 with a gap 20b therebetween. The first and second return electrodes 22a, 22b are:
When the areas of the electrodes facing the power generation unit 12 are configured to be the same, the driving voltages VA1 and VA2 having the same voltage value can be output. When the areas of the electrodes are configured to be different, the ratios of the areas are determined. The drive voltages VA1 and VA2 having the voltage values can be output.

The voltage adjusting circuit 6 includes coils L ₆ and F
Constitute a chopper circuit by ETQ _6, the voltage which the series circuit of the diodes D ₆ and the capacitor C ₆ is connected in parallel to the FETs Q _6, output from the voltage control signal generation circuit 7 to the gate terminals of the FETs Q ₆ The configuration is such that a control signal VD is input.

The voltage control signal generation circuit 7 sets the adjustable reference voltage V _REF to an arbitrary value and outputs the variable power supply EV, and the waveform shaping output from the waveform shaping section 82b of the feedback circuit 8. the driving voltage VA2 is input to the positive input terminal, a variable power supply EV by a predetermined reference voltage V _RFE is input to the input terminal of the negative side, the reference voltage V _{R EF}
And a comparison operation unit OP7 for comparing the driving voltage VA2 with the driving voltage VA2 to generate a voltage control signal having a predetermined pulse width.

The feedback circuit 8 shapes and amplifies the output waveform of the feedback signal output from the first feedback electrode 22a, and outputs the drive voltage VA1 to the drive circuit 3.
2a and a waveform shaping section 82b for shaping the output waveform of the feedback signal output from the second feedback electrode 22b and outputting the drive voltage VA2 to the voltage control signal generation circuit 7.

Note that a buffer circuit may be connected between the feedback circuit 8 (or the waveform shaping units 82a and 82b) and the feedback electrode 2 (or the first and second feedback circuits 22a and 22b). This buffer circuit is capable of impedance matching with the subsequent stage, and has a feedback electrode 2,
It acts so as to prevent the influence of noise, waveform distortion, and the like superimposed on the feedback signals output from the output terminals 22a and 22b on the subsequent stage. Further, the buffer circuit can be formed by an FET. A feedback signal is input to the gate terminal of the FET, and a current flowing when the FET is turned ON / OFF is used as a drive voltage V.
A, VA1, VA2 may be output to the subsequent stage.

Next, each operation of the self-excited oscillation and the output adjustment of the power conversion device according to the present embodiment based on each of the above configurations will be described. First, when a DC voltage having a predetermined voltage value is applied from the power supply VP to the drive section 11 of the piezoelectric transformer 1 as an input voltage VB through a series circuit of the coil L ₆ , the diode D ₆ and the coil L ₆ , the piezoelectric transformer 1 A voltage having a predetermined voltage value is generated in the power generation unit 12 of the first embodiment, and the generated voltage is output from the output electrode 121 to the load 4 as an output voltage VC. When the output voltage VC is generated, a charge is generated between the surface of the power generation unit 12 and the feedback electrode 2 (22a, 22b) disposed so as to form a gap 20 (20a, 20b) opposed thereto. Is generated, and a drive voltage VA (VA1, VA2) having a potential corresponding to the stored charge amount is generated, and the drive voltage VA (VA1, VA2) is generated by the waveform shaping sections 82a, 82a.
b, the waveform of the driving circuit 3
And is fed back to the voltage control signal generation circuit 7.

The voltage control signal generating circuit 7 compares the reference voltage V _REF corresponding to the voltage value to be output from the piezoelectric transformer 1 with the drive voltage VA of the AC voltage formed by the waveform shaping section 82b. The device OP7 compares
A voltage control signal VD having a predetermined pulse width is output.

[0048] The voltage control signal VD is applied to the gate electrode of FETs Q ₆ in the voltage regulator circuit 6, the FETs Q ₆ based on the pulse width of the voltage control signal VD is driven and controlled. The FETs Q ₆ from that forms a chopper circuit together with the coil L _6, boosts the DC voltage from the power source VP to a predetermined voltage.

The DC voltage VP ₁ thus boosted is input to the drive circuit 3, and this drive circuit 3
To re-enter to the piezoelectric transformer 1 and converts the DC voltage VP ₁ which is input based on the drive voltage VA1 which is fed back to waveform shaping in the input voltage VB of the alternating voltage 2a.

As described above, the output voltage VC of the piezoelectric transformer 1
Can be adjusted to an arbitrary voltage value without connecting an additional circuit such as an oscillator.
The voltage transformer 1 detects the voltage related to the voltage generated in the power generation unit 12 of the piezoelectric transformer 1 without affecting the voltage, and feeds this voltage back to the drive circuit 3 as the drive voltage VA1.
Can be driven by self-excited oscillation. Furthermore, the drive voltage VA1 that is fed back to the drive circuit 3 and the drive voltage VA2 that is output to the voltage control signal generation circuit 7 are opposed to each other in a non-contact manner in which the power generation unit 12 of the piezoelectric transformer 1 is separated from the power generation unit 12 by a gap 20 at a predetermined interval d. Since the detection is performed by the disposed return electrodes 2 (22a, 22b), the piezoelectric characteristics of the piezoelectric transformer 1 are not hindered.

In each of the above embodiments, a secondary Rosen-type piezoelectric transformer is used. However, another method such as a symmetric tertiary Rosen-type piezoelectric transformer or a thickness-width lateral-effect piezoelectric transformer is used. It can also be configured. In either case, the feedback electrode is disposed on one side or both sides of the power generation unit in the piezoelectric transformer with a predetermined space therebetween in a state of facing each other.

[0052]

As described above, according to the present invention, the driving means converts a DC voltage into an AC voltage based on a control signal,
This AC voltage is applied as an input voltage to an input electrode in a driving section of the piezoelectric transformer to output an output voltage from an output electrode in a power generation section of the piezoelectric transformer, and a predetermined distance from a front surface and / or a rear surface of the power generation section of the piezoelectric transformer. Because the return electrode disposed apart detects the charge corresponding to the output voltage and feeds it back to the driving means as a control signal, the control signal is output without affecting the output voltage output to the load side. The self-excited oscillation drive of the piezoelectric transformer can be generated, and the control signal can be generated without directly attaching the electrode to the piezoelectric transformer, so that the vibration of the piezoelectric transformer is not disturbed and the reliability of the device itself is improved. To play. Further, in the present invention, the piezoelectric transformer is housed in the first and second support members made of a plate-shaped member, and the elastically projecting support protrusions project from the inner surfaces of the first and second support members. Since the vibrating nodes of the piezoelectric transformer are sandwiched and the output voltage generated in the power generating section of the piezoelectric transformer is detected by the feedback electrodes provided on the first and second support members, the dielectric functioning as the power generating section is obtained. By interposing a plate-shaped member serving as a first or second support member, which is an insulator, between the body and the electrode, the charge capacity accumulated between the dielectric and the electrode is increased, and a large feedback signal is generated. Feedback can be provided, and there is an effect that self-excited oscillation driving can be performed without disturbing the vibration of the piezoelectric transformer as much as possible. Further, in the present invention, the voltage control signal generation means generates a voltage control signal based on the control signal of the feedback means, and the voltage adjustment means adjusts the voltage level of the DC voltage supplied from the power supply according to the voltage control signal. Output to the drive means, so that a voltage control signal for adjusting the output voltage of the piezoelectric transformer can be generated by a part of the feedback circuit without providing a separate output adjustment circuit including an oscillator or the like. This has the effect that the circuit configuration can be simplified without obstructing the vibration of. Also, in the present invention, since the comparison operation unit compares the voltage value of the reference voltage set by the voltage setting unit with the AC control signal output from the feedback unit, the voltage control signal is generated. The ratio of the ON state (pulse width) to the ON / OFF cycle of the voltage adjusted by the voltage adjusting means based on the setting of the reference voltage of the voltage setting unit can be controlled, and the output adjustment of the piezoelectric transformer having a predetermined step-up ratio can be performed. Can be easily performed.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of a power conversion device according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a power conversion device according to a second embodiment of the present invention.

FIG. 3 is an exploded perspective view of the power converter shown in FIG.

FIG. 4 is a view showing a case where the exploded perspective view shown in FIG. 3 is combined;
FIG. 4 is a cross-sectional view taken along a line A.

FIG. 5 is a circuit configuration diagram of a power conversion device according to a third embodiment of the present invention.

FIG. 6 is a block circuit configuration diagram of a power conversion device according to a fourth embodiment of the present invention.

FIG. 7 is a detailed circuit configuration diagram of the power converter shown in FIG.

FIG. 8 is a drive circuit diagram of a conventional piezoelectric transformer.

FIG. 9 is a circuit configuration diagram of a conventional power converter.

FIG. 10 is a circuit configuration diagram of another conventional power converter.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 piezoelectric transformer 2 feedback electrode 3, 300 drive circuit 4 load 5 storage case 5 a first support member 5 b second support member 6 voltage adjustment circuit 7 voltage control signal generation circuit 8 feedback circuit 11 drive unit 12 power generation unit 20, 20a, 20b Gap 82 Return portion 21, 21a, 21b, 22a, 22b Return electrode 50 Storage recess 51, 52, 55, 56 Node support protrusion 53a, 53b, 53c, 53d Width support protrusion 54a, 54b Longitudinal support protrusion 57 semiconductor chip 58 input and output terminals 82a, 82b, 83, the waveform shaping section 111, 112 input electrode 121 output electrode 121a lead wire 122 smoothing capacitor 301,302, Q _31, Q ₃₂ bipolar transistor 400 for oscillation IC element 407 a variable resistor L ₃ , L ₆ coil Q ₃ , Q ₆ FET d Predetermined interval

Claims (4)

[Claims] A driving unit and a power generation unit are provided on a polarized plate-shaped dielectric, and an input voltage is applied between a pair or a plurality of pairs of input electrodes provided in the driving unit, and the power generation unit is provided. In a power converter having a piezoelectric transformer configured to extract an output voltage from an output electrode provided in a power supply, a DC voltage supplied from a power supply is converted into an AC voltage according to a feedback signal given to the control electrode, and Driving means for applying the converted AC voltage to the dielectric input electrode as the input voltage; and a surface of a power generation unit in the plate-shaped piezoelectric transformer and / or
Or a feedback electrode disposed opposite to the back surface at a predetermined interval; and a charge accumulated between the feedback electrode and the front and / or back surface of the power generation unit is fed back to the control electrode of the driving unit as a feedback signal. A power conversion device comprising: 2. The power converter according to claim 1, wherein the first support member is a plate-shaped member having a storage recess capable of storing a plate-shaped piezoelectric transformer, and the first support member is stored. A second support member made of a plate-like member closing an opening of the concave portion, wherein the first support member and / or the second support member have elasticity at a position corresponding to a vibration node of the piezoelectric transformer. The return electrode is provided at a position of the first support member and / or the second support member corresponding to a power generation unit of the piezoelectric transformer, and the piezoelectric protrusion is provided by the support protrusion. A power converter characterized in that an output voltage generated in a power generation section is detected by said feedback electrode by sandwiching said vibrating node portion. 3. The power converter according to claim 1, wherein the voltage is connected to a subsequent stage of the feedback unit and generates and outputs a voltage control signal based on a feedback signal fed back from the feedback unit. A control signal generation unit, connected to a preceding stage of the driving unit, and adjusting a voltage level of a DC voltage supplied from a power supply according to a voltage control signal output from the voltage control signal generation unit; A power converter, comprising: a voltage adjusting unit that outputs a DC voltage to the driving unit. 4. The power converter according to claim 3, wherein the voltage control signal generating unit adjusts and sets a voltage value of a reference voltage, and the set reference voltage and the feedback. And a comparison operation unit for comparing the AC feedback signal output from the means to generate a voltage control signal.