JP2005184896A - Drive circuit of piezo-electric transformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the complication of a manufacturing process and a structure while forming a configuration which can perform a self oscillation without impeding the oscillation of a piezo-electric transformer. <P>SOLUTION: A drive circuit 10 of the piezo-electric transformer performs the self oscillation by feeding back a control signal So in response to the output of the piezo-electric transformer 20, and applies the drive voltage Vd of its oscillating frequency to the piezoelectric transformer 20. The drive circuit 10 includes a voltage detecting electrode 11 for detecting the control signal So in response to the output of the piezo-electric transformer 20. The voltage detecting electrode 11 is formed together with wiring 31 on a printed circuit substrate 30 on which the piezo-electric transformer 20 is mounted. Since the voltage detecting electrode 11 is formed simultaneously together with the wiring 31 of the printed circuit substrate 30, another process is not necessary to be provided as for forming the voltage detecting electrode 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a piezoelectric transformer that transforms an AC voltage using a resonance phenomenon of a piezoelectric vibrator, and more particularly to a drive circuit thereof.

  A piezoelectric transformer (solid former) is configured to input a low voltage and output a high voltage by utilizing a resonance phenomenon of a piezoelectric vibrator. The feature of the piezoelectric transformer is that the energy density of the piezoelectric vibrator is higher than that of the electromagnetic type. Therefore, since it can be downsized, it is used for cold cathode tube lighting, liquid crystal backlight lighting, small AC adapter, small high voltage power supply and the like.

  In addition, as a drive circuit for the piezoelectric transformer, an electrode is attached to the storage case of the piezoelectric transformer, and the electric charge corresponding to the output voltage of the piezoelectric transformer is detected from this electrode and fed back to the drive means as a control signal, thereby self-oscillation The technique made to do is known (patent document 1). According to this drive circuit, since a control signal can be generated without attaching an electrode directly to the piezoelectric transformer, there is an advantage that vibration of the piezoelectric transformer is not hindered.

JP-A-10-127059

  However, the drive circuit disclosed in Patent Document 1 has the following problems.

  A process for forming electrodes in the storage case, a structure for connecting the electrodes to the printed wiring board, and the like are required. This complicates the manufacturing process and structure, leading to higher prices.

  Further, depending on the phase difference of the control signal to be fed back, the positive feedback is not performed, so that self-excited oscillation may be hindered. In such a case, it is necessary to separately provide a component for setting the phase difference to a desired value.

  Accordingly, an object of the present invention is to reduce the complexity of the manufacturing process and structure while suppressing the vibration of the piezoelectric transformer without inhibiting the vibration of the piezoelectric transformer, and to control the control signal without using other components. It is an object of the present invention to provide a piezoelectric transformer driving circuit capable of setting a phase difference to a desired value.

The drive circuit according to the present invention feeds back a control signal corresponding to the output of the piezoelectric transformer and self-oscillates, and applies a drive voltage of the oscillation frequency to the piezoelectric transformer. Control according to the output of the piezoelectric transformer A voltage detection electrode for detecting a signal is provided. The voltage detection electrode is formed together with the wiring on a printed wiring board on which the piezoelectric transformer is mounted.
This voltage detection electrode has one of the following functions. (1). A voltage electrostatically induced by the output voltage of the piezoelectric transformer is detected as a control signal. (2) A voltage electromagnetically induced by the output current of the piezoelectric transformer is detected as a control signal. (3) A voltage electrostatically induced by the output voltage of the piezoelectric transformer and a voltage electromagnetically induced by the output current of the piezoelectric transformer are detected as control signals.

  Since the voltage detection electrode is formed simultaneously with the wiring of the printed wiring board, it is not necessary to provide a separate process for forming the voltage detection electrode. In addition, since the connection between the voltage detection electrode and the wiring of the printed wiring board is made at the same time when the wiring is formed, a separate process is not required and the structure is simple.

  According to a fourth aspect of the present invention, in the driving circuit according to the first to third aspects, the piezoelectric transformer is mounted on one surface of the printed wiring board, and the voltage detection is performed opposite the piezoelectric transformer on the other surface of the printed wiring board. An electrode is formed.

  The piezoelectric transformer and the voltage detection electrode are opposed to each other with the printed wiring board interposed therebetween. Therefore, the creeping distance between the piezoelectric transformer and the voltage detection electrode is the distance from the piezoelectric transformer on one side of the printed wiring board to the voltage detection electrode on the other side of the printed wiring board through the peripheral edge of the printed wiring board. From long enough. Therefore, the insulation between the piezoelectric transformer and the voltage detection electrode is good.

  The drive circuit according to claim 5 is the drive circuit according to any one of claims 1 to 4, wherein an output current detector for detecting an output current of the piezoelectric transformer and an oscillator for oscillating at a frequency of a control signal detected by the voltage detection electrode. A duty ratio control unit that controls the duty ratio of the drive voltage according to the output current detected by the output current detection unit, and a piezoelectric transformer that converts the drive voltage according to the frequency in the oscillation unit and the duty ratio controlled by the duty ratio control unit. And a drive unit to be applied.

  The oscillation unit oscillates at the same frequency as the frequency of the control signal. The duty ratio control unit controls the duty ratio of the drive voltage according to the output current. The drive unit applies a drive voltage to the piezoelectric transformer at a frequency and a controlled duty ratio in the oscillation unit. The duty ratio control unit may increase the duty ratio by increasing the duty ratio if the output current is large (that is, by increasing the voltage application time of the piezoelectric transformer), and increase the power supplied to the load if the power consumption at the load increases. it can. Conversely, if the output current is large, the duty ratio can be reduced (that is, the voltage application time of the piezoelectric transformer can be shortened), whereby the power consumption at the load can be made constant.

  The drive circuit according to claim 6 is the drive circuit according to claims 1 to 5, wherein the voltage detection electrode has a shape to which a coil component for setting the phase difference of the control signal to a predetermined value is applied. That's it.

  The voltage detection electrode is provided with a coil component by a shape as described later. In general, it is considered that the phase of the control signal is delayed as the coil component is applied, but it is not so simple because it varies depending on the size and position of the voltage detection electrode. Actually, the relationship between the shape of the voltage detection electrode and the phase difference of the control signal is measured in advance, and the shape of the voltage detection electrode is selected so that a desired phase difference is obtained.

  The drive circuit according to any one of claims 7 to 9 is the drive circuit according to any one of claims 1 to 5, wherein the voltage detection electrode is specified to have a polygonal shape, a circular shape, an elliptical shape, a spiral shape, a frame shape, or the like. The polygon is an N-gon when N is an integer of 3 or more. The spiral shape includes a polygonal spiral, a circular spiral, an elliptical spiral, and the like. The frame shape includes a polygonal frame, a circular frame, an elliptical frame, and the like.

  When the voltage detection electrode has a polygonal shape, a circular shape, or an elliptical shape, it does not include a coil component, which is suitable for detecting an electrostatic induction voltage. When the voltage detection electrode has a spiral shape, it contains many coil components and is suitable for detecting an electromagnetic induction voltage. When the shape of the voltage detection electrode is a frame shape, since it includes a little more coil components, it is suitable for detecting a voltage in which both electrostatic induction voltage and electromagnetic induction voltage are mixed. In addition, when many coil components are included, the electromagnetic induction voltage is proportional to the frequency of the output current of the piezoelectric transformer according to Faraday's law of electromagnetic induction, so that the detection sensitivity improves as the frequency becomes higher.

  According to the drive circuit of the present invention, the voltage detection electrode for detecting the control signal for self-excited oscillation is formed on the printed wiring board on which the piezoelectric transformer is mounted together with the wiring, thereby forming the wiring of the printed wiring board. They can be formed simultaneously in the process. In addition to this, the connection between the voltage detection electrode and the wiring of the printed wiring board is made at the same time when the wiring is formed, so that another process is unnecessary and the structure is simple. Therefore, it is possible to suppress the complexity of the manufacturing process and the structure while being configured to be capable of self-oscillation without hindering the vibration of the piezoelectric transformer. Moreover, according to the drive circuit which concerns on this invention, there exists the following effect for every claim.

  According to the drive circuit of the fourth aspect, since the piezoelectric transformer and the voltage detection electrode are opposed to each other with the printed wiring board interposed therebetween, the piezoelectric transformer and the voltage detection electrode can be connected to each other even if the piezoelectric transformer and the voltage detection electrode are brought close to each other. Therefore, the insulation between the piezoelectric transformer and the voltage detection electrode can be improved without impairing the sensitivity of the voltage detection electrode.

  According to the drive circuit of the fifth aspect, by applying a drive voltage to the piezoelectric transformer at the same frequency as the control signal and a duty ratio controlled according to the output current of the piezoelectric transformer, a wide variety can be obtained according to the output current. Control, for example, control that makes the power consumption at the load constant can be realized.

  According to the drive circuit of the sixth aspect, the phase difference of the control signal can be set to a desired value without using other components by using the shape of the voltage detection electrode provided with the coil component corresponding to the phase difference of the control signal. Can be set to a value.

  According to the drive circuit of the seventh aspect, since the voltage detection electrode including no coil component can be obtained by making the shape of the voltage detection electrode polygonal, circular or elliptical, the electrostatic induction voltage can be detected. A suitable voltage detection electrode can be realized.

  According to the drive circuit of the eighth aspect, since the voltage detection electrode containing a large amount of coil components can be obtained by making the voltage detection electrode spiral, the voltage detection electrode suitable for detecting the electromagnetic induction voltage is realized. it can.

  According to the drive circuit of the ninth aspect, since the voltage detection electrode including a little more coil component can be obtained by making the shape of the voltage detection electrode into a frame shape, it is suitable for detection of electrostatic induction voltage and electromagnetic induction voltage. A voltage detection electrode can be realized.

  FIG. 1 shows an embodiment of a drive circuit according to the present invention. FIG. 1 [1] is a circuit configuration diagram, FIG. 1 [2] is a plan view of a voltage detection electrode, and FIG. 1 [3] is FIG. ] Is a sectional view taken along line I-I in FIG. Hereinafter, description will be given based on this drawing.

  The drive circuit 10 according to the present embodiment feeds back a control signal So corresponding to the output of the piezoelectric transformer 20 to self-oscillate, and applies a drive voltage Vd having the oscillation frequency to the piezoelectric transformer 20. The voltage detection electrode 11 which detects the control signal So according to the output of is provided. The voltage detection electrode 11 is formed together with the wiring 31 on the printed wiring board 30 on which the piezoelectric transformer 20 is mounted.

  The piezoelectric transformer 20 is provided with primary electrodes 22 and 23 and a secondary electrode 24 on a piezoelectric vibrating body 21, the primary side is polarized in the thickness direction (the vertical direction in FIG. [1]), and the secondary side in the length direction ( They are polarized in the figure [2] left and right direction) and accommodated in the resin case 25. The primary electrodes 22 and 23 are opposed to each other with the piezoelectric vibrator 21 interposed therebetween. The piezoelectric vibrating body 21 is made of piezoelectric ceramics such as PZT and has a plate shape (cuboid shape). In the longitudinal direction of the piezoelectric vibrator 21, primary electrodes 22 and 23 are provided from one end to half of the length, and a secondary electrode 24 is provided at the other end. When the drive voltage Vd having the natural resonance frequency fr determined by the length dimension is input to the primary side, strong mechanical vibration is caused by the inverse piezoelectric effect, and a high output voltage Vo corresponding to the vibration is output from the secondary side by the piezoelectric effect. . The output voltage Vo is applied to the load 40.

  The voltage detection electrode 11 has one of the following functions depending on its shape and the like which will be described later. (1). A voltage electrostatically induced by the output voltage Vo of the piezoelectric transformer 20 is detected as a control signal So. (2) The voltage electromagnetically induced by the output current Io of the piezoelectric transformer 20 is detected as the control signal So. (3) The voltage electrostatically induced by the output voltage Vo of the piezoelectric transformer 20 and the voltage electromagnetically induced by the output current Io of the piezoelectric transformer 20 are detected as the control signal So.

  The printed wiring board 30 is a general one composed of an insulating plate 32, a conductor film 33, an insulating film 34, and the like. The insulating plate 32 and the insulating film 34 are made of synthetic resin, for example. The conductor film 33 is, for example, a copper foil, and is processed into a predetermined shape to become the wiring 32 or the voltage detection electrode 11. Although not shown, a conductive film and an insulating film are provided on the surface 35 of the insulating plate 32, components (not shown) of the piezoelectric transformer 20 and the drive circuit 20 are mounted, and wiring (not shown) is also formed. ing. Wirings 32 and voltage detection electrodes 11 are formed on the back surface 36 of the insulating plate 32, and these are covered with an insulating film 34. However, in FIG. 1 [2], the insulating film 34 is omitted.

  Next, a method for forming the wiring 32 and the voltage detection electrode 11 on the printed wiring board 30 will be described. First, an insulating plate 32 having a conductor film 33 formed on the entire surface is prepared. Then, the conductor film 33 is processed into a predetermined shape using, for example, photolithography and etching, and the wiring 32 and the voltage detection electrode 11 are obtained. Finally, the wiring 32 and the voltage detection electrode 11 are covered with an insulating film 34 except for the soldered portion of the wiring 32.

  Thus, since the voltage detection electrode 11 is formed simultaneously with the wiring 31 of the printed wiring board 30, it is not necessary to provide another process for forming the voltage detection electrode 11. In addition, since the connection between the voltage detection electrode 11 and the wiring 31 of the printed wiring board 30 is made at the same time when the wiring 31 is formed, a separate process is unnecessary and the structure is simple. Therefore, according to the drive circuit 10 of the present embodiment, it is possible to suppress the complexity of the manufacturing process and the structure while having a configuration capable of self-oscillation without inhibiting the vibration of the piezoelectric transformer 20.

  In the present embodiment, the piezoelectric transformer 20 is mounted on one surface of the printed wiring board 30, and the voltage detection electrode 11 is formed on the other surface of the printed wiring board 30 so as to face the piezoelectric transformer 20. That is, the piezoelectric transformer 20 and the voltage detection electrode 11 are opposed to each other with the printed wiring board 30 interposed therebetween. Therefore, the creeping distance between the piezoelectric transformer 20 and the voltage detection electrode 11 is the distance L1 from the piezoelectric transformer 20 to the peripheral end 37 of the printed wiring board 30, the thickness of the printed wiring board 30, and the voltage detection electrode 11 to the printed wiring board. Since it is the sum of the distance L2 to 30 peripheral ends 37, it is sufficiently long. Therefore, according to the drive circuit 10 of the present embodiment, the creeping distance between the piezoelectric transformer 20 and the voltage detection electrode 11 can be sufficiently increased even when the piezoelectric transformer 20 and the voltage detection electrode 11 are brought close to each other. The insulation between the piezoelectric transformer 20 and the voltage detection electrode 11 can be improved without impairing the sensitivity.

  FIG. 2 is a plan view showing the shape of the voltage detection electrode in this embodiment. FIG. 2 [1] is an example of a polygonal shape, FIG. 2 [2] is an example of a spiral shape, and FIG. 2 [3] is a frame shape. It is an example. Hereinafter, description will be given based on this drawing.

  The shape of the voltage detection electrode 111 in FIG. 2 [1] is a square shape. Since this shape does not include a coil component, it is suitable for detecting an electrostatic induction voltage. The same applies to other polygonal shapes, circular shapes, or elliptical shapes.

  The shape of the voltage detection electrode 112 in FIG. 2 [2] is a square spiral. Since this shape includes many coil components, it is suitable for detecting an electromagnetic induction voltage. The same applies to other polygonal spirals, circular spirals, or elliptical spirals. In general, the coil component increases as the number of turns increases.

  The shape of the voltage detection electrode 113 in FIG. 2 [3] is a square frame. Since this shape includes a little more coil components, it is suitable for detecting a voltage in which both electrostatic induction voltage and electromagnetic induction voltage are mixed. The same applies to other polygonal frames, circular frames, or elliptical frames.

  Further, the phase difference of the control signal So can be set to a predetermined value by changing the coil component to be applied like the voltage detection electrodes 111 to 113. In general, it is considered that the phase of the control signal So is delayed as the coil component is applied, but it is not so simple because it is affected by the size and mounting position of the voltage detection electrodes 111 to 113. Actually, the relationship between the shape of the voltage detection electrodes 111 to 113 and the phase difference of the control signal So is measured in advance, and the shape of the voltage detection electrodes 111 to 113 is selected so that a desired phase difference is obtained.

  Furthermore, when many coil components are included, the electromagnetic induction voltage is proportional to the frequency of the output current Io of the piezoelectric transformer 20, so that the detection sensitivity improves as the frequency becomes higher.

  3 and FIG. 4 show an example in which the above embodiment is further embodied, FIG. 4 is a circuit diagram showing the overall configuration, and FIG. 4 is a waveform diagram showing waveforms in each part of FIG. Hereinafter, description will be given based on this drawing. However, the same parts as those in FIG. In FIG. 3 and FIG. 4, the alphanumeric characters in circles are displayed as alphanumeric characters in parentheses in the specification. Also, the portions (1) to (9) in FIG. 3 correspond to the waveforms in FIGS. 4 (1) to (9), respectively.

  The drive circuit 10 of the present embodiment oscillates at the frequency of the voltage detection electrode 11 described above, the output current detection unit 12 that detects the output current Io of the piezoelectric transformer 20, and the control signal So detected by the voltage detection electrode 11. The oscillation unit 13 is controlled by a duty ratio control unit 14 that controls the duty ratio of the drive voltage Vd according to the output current Io detected by the output current detection unit 12, and the frequency and duty ratio control unit 14 in the oscillation unit 13. And a drive unit 15 that applies the drive voltage Vd to the piezoelectric transformer 20 according to the duty ratio.

  The drive circuit 10 is additionally provided with a resonance unit 16 as a part of the drive unit 15, a reference voltage generation unit 17 that generates a reference voltage, and the like. A DC input voltage Vin is applied to the input side of the drive circuit 10, and a capacitor C1 for preventing voltage fluctuation is connected between the input terminals. On the output side of the piezoelectric transformer 20, rectifying diodes D3 and D4, a smoothing capacitor C8, and resistors R19 and R20 associated therewith are attached. Further, a load 40 is connected to these output sides.

  The voltage detection electrode 11 detects a voltage electrostatically induced by the output voltage Vo of the piezoelectric transformer 20 as a control signal So.

  The reference voltage generation unit 17 includes a resistor R3, a Zener diode D1, a capacitor C2, and the like, and receives the input voltage Vin and outputs a reference voltage.

  The oscillation unit 13 includes resistors R6 to R11, a capacitor C3, a comparator IC1, and the like. The control signal So (waveform (1)) detected by the voltage detection electrode 11 is applied to the + input terminal of the comparator IC1. The average voltage (waveform (2)) of the output voltages (waveform (7)) of the transistors Q1 and Q2 is applied to the negative input terminal of the comparator IC1. Thereby, the comparator IC1 outputs a rectangular wave signal (waveform (3)) that oscillates at the frequency of the control signal So.

  The output current detection unit 12 includes a resistor R4, a capacitor C5, a transistor Q5, and the like. Resistor R4 and capacitor C5 generate a base voltage of transistor Q5 corresponding to output current Ii. When the base voltage exceeds the threshold voltage, transistor Q5 is turned on. Then, the collector-emitter voltage of the transistor Q5 decreases as the base voltage increases. Further, an adjusting variable resistor may be connected in parallel to the resistor R4. The detailed operation of the output current detection unit 12 will be described later.

  The duty ratio control unit 14 includes resistors R15 to R17, a capacitor C6, a comparator IC2, an FET Q4, and the like. A voltage (waveform (5)) obtained by dividing the reference voltage by the resistors R15 and R16 and the transistor Q5 of the output current detection unit 12 is applied to the negative input terminal of the comparator IC2. This voltage (waveform (5)) corresponds to the output current Io of the piezoelectric transformer 20. That is, when the output current Io exceeds a certain value, the voltage (waveform (5)) decreases as the output current Io increases. On the other hand, a sawtooth voltage (waveform (4)), which is an integral waveform of the output voltages (waveform (7)) of the transistors Q1 and Q2, is applied to the + input terminal of the comparator IC2. Thereby, the comparator IC2 outputs a duty ratio signal (waveform (6)) corresponding to the output current Io. The duty ratio signal (waveform (6)) is applied to the gate of the FET Q4. When the FET Q4 is turned on, the FET Q3 of the drive unit 15 is forcibly turned off. That is, the drain voltage of the FET Q4 becomes the gate voltage of the FET Q3 (waveform (8)).

  The drive unit 15 includes resistors R12 to R14, transistors Q1 and Q2, FET Q3, and the like. The resonance unit 16 includes a coil L1, a capacitor C4, and the like. The transistors Q1 and Q2 constitute a complementary circuit and function as a buffer for the comparator IC1 (waveform (7)). The FET Q3 is turned on / off according to the output voltage (waveform (7)) of the transistors Q1 and Q2 when the FET Q4 is off, and is always off when the FET Q4 is on. The values of the coil L1 and the capacitor C4 are set so as to resonate with the internal capacitance of the piezoelectric transformer 20. Therefore, when the FET Q3 is turned from on to off, the drive voltage Vd is applied to the piezoelectric transformer 20 (waveform (9)).

  The time ton when the FET Q3 is turned on is the rise time (b) of the duty ratio signal (waveform (6)) output from the comparator IC2 from the rise time (a) of the output voltage (waveform (7)) of the transistors Q1 and Q2. Up to. Conversely, the time toff when the FET Q3 is turned off is from the rise time (b) of the duty ratio signal (waveform (6)) to the next rise time (a) of the output voltage (waveform (7)). Here, since the duty ratio is ton / (ton + toff), it can be set to a desired value by controlling the rise time (b) of the duty ratio signal (waveform (6)).

  Next, the overall operation of the drive circuit 10 will be described.

  The oscillator 13 oscillates at the same frequency as that of the control signal So. The duty ratio control unit 14 controls the duty ratio of the drive voltage Vd according to the output current Io. The drive unit 15 applies the drive voltage Vd to the piezoelectric transformer 20 at the frequency and controlled duty ratio in the oscillation unit 13. At this time, when the output current Io exceeds a certain value, the duty ratio control unit 14 reduces the duty ratio if the output current Io is large (that is, by shortening the voltage application time of the piezoelectric transformer 20). The power consumption at the load 40 can be made constant.

  FIG. 5 is an explanatory diagram showing the operation of the output current detection unit in FIG. 3. FIG. 5 [1] is a circuit diagram (part 1), FIG. 5 [2] is a circuit diagram (part 2), and FIG. Is a waveform diagram. Hereinafter, description will be given based on this drawing. However, the same parts as those in FIG.

First, as shown in FIG. 5 [1], the electric charge charged in the capacitor C8 by the piezoelectric transformer 20 is discharged as a current I _R = I _R1 + I _R2 . Therefore, correspondingly to the electric charge charged in the capacitor C8 is discharged by the current I _R, it is necessary to supply a new charge from the piezoelectric transformer 20.

Accordingly, Figure 5 [2], as shown in [3], to charge an internal volume 20C to the current _{I A} of the piezoelectric transformer 20 in the first half-wave. Subsequently, to charge the capacitor C8 in the current I _B including the charge of the internal volume 20C of the piezoelectric transformer 20 in the remaining half-waves. Here, since the output of the piezoelectric transformer 20 is a sine wave, the charge / discharge currents are the same, so that I _A = I _B = I _R holds.

Accordingly, the current I _A flowing to the resistor R4 is is equal to the current I _R flowing through the load 40 side, a voltage drop or base voltage of the transistor Q5 in the resistor R4 becomes the detected value of the current I _R.

1 shows an embodiment of a drive circuit according to the present invention, FIG. 1 [1] is a circuit configuration diagram, FIG. 1 [2] is a plan view of a voltage detection electrode, and FIG. 1 [3] is I-- in FIG. It is I sectional drawing (a piezoelectric transformer side is shown above). FIG. 2 is a plan view showing the shape of the voltage detection electrode in FIG. 1, FIG. 2 [1] is an example of a polygonal shape, FIG. 2 [2] is an example of a spiral shape, and FIG. 2 [3] is an example of a frame shape. 1 is a circuit diagram showing an overall configuration in an embodiment of a drive circuit according to the present invention. It is a wave form diagram which shows the waveform in each part of FIG. FIG. 5 is an explanatory diagram showing the operation of the output current detection unit in FIG. 3, in which FIG. 5 [1] is a circuit diagram (part 1), FIG. 5 [2] is a circuit diagram (part 2), and FIG. It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drive circuit 11,111,112,113 Voltage detection electrode 12 Output current detection part 13 Oscillation part 14 Duty ratio control part 15 Drive part 16 Resonance part 17 Reference voltage generation part 20 Piezoelectric transformer 30 Printed wiring board 31 Wiring So Control signal Vd Drive voltage Io Output current Vo Output voltage

Claims (9)

In the piezoelectric transformer drive circuit, which feeds back a control signal according to the output of the piezoelectric transformer and self-oscillates, and applies a drive voltage of the oscillation frequency to the piezoelectric transformer.
A voltage detection electrode for detecting, as the control signal, a voltage electrostatically induced by the output voltage of the piezoelectric transformer;
On the printed wiring board on which the piezoelectric transformer is mounted, the voltage detection electrode is formed together with the wiring,
A piezoelectric transformer drive circuit characterized by the above. In the piezoelectric transformer drive circuit, which feeds back a control signal according to the output of the piezoelectric transformer and self-oscillates, and applies a drive voltage of the oscillation frequency to the piezoelectric transformer.
A voltage detection electrode for detecting a voltage electromagnetically induced by the output current of the piezoelectric transformer as the control signal;
On the printed wiring board on which the piezoelectric transformer is mounted, the voltage detection electrode is formed together with the wiring,
A piezoelectric transformer drive circuit characterized by the above. In the piezoelectric transformer drive circuit, which feeds back a control signal according to the output of the piezoelectric transformer and self-oscillates, and applies a drive voltage of the oscillation frequency to the piezoelectric transformer.
A voltage detection electrode for detecting, as the control signal, a voltage electrostatically induced by the output voltage of the piezoelectric transformer and a voltage electromagnetically induced by the output current of the piezoelectric transformer;
On the printed wiring board on which the piezoelectric transformer is mounted, the voltage detection electrode is formed together with the wiring,
A piezoelectric transformer drive circuit characterized by the above. The piezoelectric transformer is mounted on one surface of the printed wiring board, and the voltage detection electrode is formed on the other surface of the printed wiring board so as to face the piezoelectric transformer.
4. A drive circuit for a piezoelectric transformer according to claim 1. An output current detector for detecting an output current of the piezoelectric transformer;
An oscillator that oscillates at a frequency of a control signal detected by the voltage detection electrode;
A duty ratio controller that controls the duty ratio of the drive voltage according to the output current detected by the output current detector;
A drive unit that applies the drive voltage to the piezoelectric transformer according to the duty ratio controlled by the frequency and the duty ratio control unit in the oscillation unit;
The drive circuit of the piezoelectric transformer in any one of Claims 1 thru | or 4 provided with these. The voltage detection electrode has a shape provided with a coil component for setting the phase difference of the control signal to a predetermined value.
6. A drive circuit for a piezoelectric transformer according to claim 1. The voltage detection electrode has a polygonal shape, a circular shape, or an elliptical shape,
6. A drive circuit for a piezoelectric transformer according to claim 1. The voltage detection electrode has a spiral shape,
6. A drive circuit for a piezoelectric transformer according to claim 1. The voltage detection electrode has a frame shape.
6. A drive circuit for a piezoelectric transformer according to claim 1.

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