JP2000224842A - Piezoelectric high voltage power source unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a piezoelectric high voltage power source unit which can obtain a constant output with simple constitution when a load is changed, by restraining distortion of a sine wave to a driving electrode of a piezoelectric transformer with simple constitution. SOLUTION: A resonance circuit consists of an inductance L2 for resonance which is connected with a driving electrode of a piezoelectric transformer C3, a capacitor C2 for resonance which is connected in parallel with the transformer C3, and a capacitor C1 for fine adjustment of phase which is connected in parallel with a switching element Q1, and adjusts finely the phase of a sine wave in such a manner that the phase of the sine wave applied to the transformer is made to coincide with the phase of a control signal to the switching element which signal has a specified duty ratio. The frequency of a sine wave applied to the transformer C3 is determined by the resonance circuit, so that an almost perfect sine wave is always applied to the transformer C3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric high-voltage power supply device, and more particularly, to a constant voltage by maintaining a duty ratio of a sine wave to a driving electrode of a piezoelectric transformer at a predetermined ratio and changing its resonance frequency. The present invention relates to a piezoelectric high-voltage power supply that realizes low current.

[0002]

2. Description of the Related Art A flyback transformer using a winding transformer has been widely used as a power supply for an electrostatic dust collector used in an air cleaner or the like. However, since the power supply using this transformer uses a winding type, the power supply becomes large, and a layer short / line-to-line short tends to occur.

A flyback transformer has low conversion efficiency (ratio of output power to input power) (for example, 3
(About 0 to 40%).

For this reason, for example, a piezoelectric transformer (piezoelectric element) has recently been used as a power supply for an electrostatic dust collector in place of a flyback transformer.

The piezoelectric transformer includes a substrate made of a piezoelectric material mainly composed of barium titanate, lead zirconate titanate, or the like, a pair of drive electrodes sandwiching the substrate, and a rear end (side surface) of the substrate. A single output electrode is provided, and a sine-wave drive voltage is applied to both drive electrodes to excite the piezoelectric transformer at its natural frequency, thereby extracting a high voltage from the output electrode. Things.

[0006]

However, a high-voltage power supply using a piezoelectric transformer does not use a wire-wound type transformer, so it is small and does not have a layer short (so-called line-to-line short). Since the sensitivity is affected sensitively, for example, when the temperature changes and the sine wave applied to the drive electrode is distorted, there is a problem that the conversion efficiency is deteriorated and it is difficult to obtain a stable output.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a simple structure to suppress a sine wave distortion to a driving electrode of a piezoelectric transformer, and to provide a constant output even if the load fluctuates. It is an object of the present invention to obtain a piezoelectric high-voltage power supply device having a configuration.

[0008]

According to the present invention, a sine wave of a predetermined frequency is applied to a drive electrode of a piezoelectric transformer by connecting an inductance and a switching element, connecting the inductance and a switching element in series, and turning the switching element on and off. In a piezoelectric high-voltage power supply that applies a high-voltage output obtained by rectifying and amplifying an output signal obtained at the output end of a piezoelectric transformer to a load, a switching element is connected to one of the switching elements, and the other is connected to a driving electrode of the piezoelectric transformer. A phase fine tuning capacitor connected in parallel to the switching element and finely adjusting the phase of the sine wave so that the phase of the sine wave applied to the piezoelectric transformer matches the phase of the control signal to the switching element; and a parallel connection to the piezoelectric transformer. And a resonance capacitance that has been set.

For this reason, a gate control signal having a predetermined duty ratio for increasing the conversion efficiency of the piezoelectric transformer is applied to the switching element.

For example, the resonance frequency of a resonance circuit including a resonance inductance, a resonance capacitance, and an input capacitance of a piezoelectric transformer changes according to the frequency of a gate control signal (duty ratio is 1: 1). The output from the piezoelectric transformer is efficiently increased.

The frequency of the gate control signal is preferably a frequency with a magnification of more than 1 and less than 1.2 than the resonance frequency based on the capacitance of the piezoelectric transformer, the capacitance for resonance, and the inductance for resonance.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present embodiment, a load will be described as a charging section and a dust collecting section of an electrostatic dust collecting apparatus.

<First Embodiment> FIG. 1 is a schematic structural view of a piezoelectric high-voltage power supply for an electrostatic precipitator. The piezoelectric high-voltage power supply device 1 shown in FIG. 1 sucks dust-containing air, and charges dust particles in the sucked dust-containing air by a corona discharge space between a discharge electrode and a counter electrode of a charging unit (not shown). And an electrostatic force generated between the dust collecting electrode plate and the non-dust collecting electrode plate disposed in the dust collecting portion (not shown) to collect charged dust particles on the dust collecting electrode plate. It is used in the dust collector 2.

The charging unit and the dust collecting unit of the electrostatic dust collecting device 2 have internal impedances of several MΩ to several + MΩ, respectively.

In this case, the amount of charge of the charging section is proportional to the square root of the charging current, and the dust collection efficiency of the dust collecting section is proportional to the electric field strength of the dust collecting electrode plate and the non-dust collecting electrode plate (in other words, the collecting efficiency). It is proportional to the potential difference between the dust plate and the non-dust collecting plate, ie, the voltage applied to the dust collecting portion.

Therefore, the output voltage of the high-voltage power supply 1
The output current characteristic is, for example, as shown in FIG.
In the above case, the constant output voltage of about 6 kV
A high-voltage power supply having a characteristic of maintaining the output current of A and rapidly decreasing thereafter is considered to be ideal.

That is, as shown in FIG. 2, it is desirable to have a constant voltage / constant current characteristic with respect to the load line.

In FIG. 2, the temperature is -20.degree.
It shows three characteristics of 5 ° C. and 80 ° C.

The piezoelectric high-voltage power supply 1 according to the first embodiment.
Is a power supply having basically the characteristics of constant output voltage and constant output current shown in FIG. 2, and has the following configuration as shown in FIG.

In the piezoelectric high-voltage power supply device 1 shown in FIG. 1, an inductance L1 for removing ripples and a power MOSFET Q1 for chopper are connected in series to a DC power supply 5, and a capacitance C1 for fine-tuning a phase is connected in parallel to the power MOSFET Q1. Connected.

Further, the resonance inductance L2 and the resonance capacitance C2 are connected in series, and are connected in parallel to the phase fine adjustment capacitance C1.

Further, a piezoelectric transformer C3 for amplifying a sine wave inputted to the resonance capacitance C2 is connected in parallel, and an output of the piezoelectric transformer C3 is connected to a rectifier circuit 6, so that an output sine wave of the piezoelectric transformer C3 is obtained. Is obtained at the output terminals 6a and 6b.
The resonance circuit 10 of the piezoelectric transformer includes the capacitances C2 and C3 and the resonance inductance L2.

Further, the output voltage and output current of the output terminals 6a and 6b when the charging unit or the dust collecting unit (hereinafter referred to as the load 2) of the electrostatic dust collecting device 2 is connected are detected and converted into voltages. An output value detection circuit section 7 for outputting a current value to a control circuit section 8 described later is provided.

The control circuit 8 includes an output value detection circuit 7
Then, the magnitudes of the output current values and the output voltage values of the output terminals 6a and 6b are determined, and based on the result, it is determined whether the current condition of the load 2 is appropriate in the constant voltage or constant current operation region.

Then, the gate control signal fg having such a frequency that the output becomes constant according to the output voltage or the output current value.
(A rectangular wave with a duty ratio of 1: 1)
Output to Q1.

(Structure of Main Part) The piezoelectric transformer C3 is composed of a substrate made of a piezoelectric material mainly composed of barium titanate, lead zirconate titanate, etc., a pair of drive electrodes sandwiching the substrate, and a back plate. One output electrode is provided at the end (side surface), and the output characteristics change depending on the frequency, temperature, etc. of the input sine wave. Also, it changes depending on the dimensions, thickness, and the like.

The resonance circuit 10 of the piezoelectric transformer includes an inductance L2 and capacitances C2 and C3.
Has the frequency characteristics shown in FIG.

This resonance circuit 10, as shown in FIG.
In the present embodiment, the resonance point is different depending on the impedance of the load.
And 100 MΩ, the standard is 6 MΩ.

The relationship between the capacitances C2 and C3 is as follows, where the resonance frequency on the resonance circuit 10 is f2.

(Equation 1) When the gate control signal has a frequency slightly higher than f2 and a duty ratio of 1: 1, the conversion efficiency of the piezoelectric transformer C3 is good.

Assuming that the frequency of the gate control signal generated from the control circuit unit 8 is fg, the efficiency is lowered even if the frequency fg is too high.

For this reason, it is most preferable that 1 <fg / f2 <1.2.

For example, under the condition of inductance L2 = 801 [μH] C2 + C3 = 5.47 [nF] fg = 85.12 [kHz], fg / f2 = 1.12 and conversion efficiency 8
1.2% (about twice the conventional value) can be obtained. next,
The basis of these numerical values will be described with reference to Tables 1 and 2.

[0033]

[Table 1]

[Table 2] As shown in these tables, at L2, 100 [μ
H], the efficiency drops sharply, and 2000 [μH]
Beyond this, the efficiency becomes extremely poor.

Also, for (C2 + C3), 3 [n
F] is 40% and the efficiency is 8.95% at 2 [nF].
And extremely low.

Also, when the value exceeds 40 [nF] and reaches 50 [nF]
In this case, it is 16.3%. As described above, the range of 100 [μH] <L2 <2000 [μH] 3 [nF] <C2 + C3 <40 [nF] is desirable.

From the above, the conversion efficiency was highest in the present embodiment when the inductance L2 = 801 [μH] C2 + C3 = 5.47 [nF] fg = 85.12 [kHz].

It is also known that the efficiency of L1 C1 does not have any adverse effect on the condition of L1> 2 [mH].

As for C1, 3 [nF] <C1
It may be in the range of <15 [nF].

The configurations of the output value detection circuit section 7 and the control circuit section 8 will be described with reference to FIG. The output value detection circuit unit 7 includes an output voltage detection circuit 15 and an output current detection circuit 16, as shown in FIG.

As shown in FIG. 4, the output voltage detection circuit 16 includes at least a resistor R1 (in this embodiment, 200M
Ω) and resistors R2 and R3 (200 k in this embodiment).
Ω) to divide the output voltage Vi, and divide this divided value into A
The detection output voltage VK amplified by MP1 is sent to the control circuit unit 8.

As shown in FIG. 4, the output current detection circuit 16 connects the load 2 and the resistor R5 (6 kΩ in the present embodiment) in series, and outputs the output voltage Vi to the load 2 via the resistor R5. The voltage of the applied current is detected by the voltage follower AMP 2, and the output current value VA is output to the control circuit 8.

As shown in FIG. 4, the control circuit section 8 includes a magnitude judgment circuit 20, a constant voltage control circuit 21, a constant current control circuit 22, and a VF conversion circuit 23.

The magnitude determination circuit 20 includes an output value detection circuit 7
The detected output voltage VK detected by the output voltage detecting circuit 15 is compared with the voltage corresponding to the detected current value VA detected by the output current detecting circuit 16. If the detected current value VA is larger, Is determined to be in the lower right region (hatched region in the figure) of the 6MΩ load line shown in FIG. 5, and the constant current control circuit 22 is operated to obtain a constant current output (for example, 1 mA).

If the detected output voltage VK is higher or equal, it is determined that the detected output voltage VK is in the upper left area (the area not hatched in the figure) of the 6MΩ load line, and the constant voltage control circuit 21 is operated. Constant output voltage (for example,
6 kV).

Specifically, the detection output voltage VK is applied to the resistor R7.
And the output current value VA is input to the resistor R8, and AM
P3 compares both voltages.

The voltage of the comparison result is AMP4,
Chattering is prevented by a hysteresis circuit including a transistor Q2 and the like.

For example, in the case of a resistive load, as shown in FIG. 5, when the impedance of the load 2 changes from 6 MΩ to 3 MΩ or 12 MΩ, control is performed so that the load 2 smoothly rides on the load line. In FIG. 5, each load line is shown as a straight line because the load is a resistance load.
Depending on the load (the charging unit or the dust collecting unit of the electrostatic precipitator), the load line may be a parabolic load line instead of a straight line.

The constant voltage control circuit 21 obtains a constant voltage output by the resistors R10 to R16 and AMP4 as shown in FIG. 6, and the resistor R11 has a voltage of 6 V (corresponding to 6 kV).
, The detection output voltage VK is input to the resistor R10, and the voltage value obtained by amplifying the difference between the two voltages is obtained as VOPV.

For example, the VOPV characteristic shown in FIG. 7A is obtained. Then, an output VFV divided by the resistors R14, R15, and R16 is obtained. This VFV has characteristics as shown in FIG.

As shown in FIG. 8, the low current control circuit 22 obtains a constant current output by the resistors R20 to R26 and AMP5, and inputs the voltage V base I corresponding to the reference current to the resistor R20. Then, the detection output current value VA is input to the resistor R21, and a voltage value V _opI obtained by amplifying the difference between the two is obtained.

For example, the V _opI characteristics shown in FIG. _9A are obtained. Then, an output VFI divided by the resistors R24, R25 and R26 is obtained. This VFI has characteristics as shown in FIG.

As shown in FIG. 10, the VF conversion circuit 23 includes resistors R36 to R43, a capacitor C4,
C5, CP9, diodes D7, D8, D9, D10,
Consisting of transistors Q6, Q7, NAND1, 2 etc.
An output VFV from the constant voltage control circuit 21 or an output VFI from the constant current control circuit 22 is input to CP9, the resistor R40, the collector of the transistor Q6, and the power supply of the NAND1,
A gate control signal fg having a duty ratio of 1: 1 (for example, a frequency of about 85 kHz) is generated.

Further, when a high voltage (for example, 3 to 6 kV) output voltage Vi is applied to the charging section of the load 2, a corona discharge space is formed, and the dust particles passing through the charging section are charged.

When a high voltage (for example, 3 to 6 kV) output voltage Vi is applied to the dust collecting portion of the load 2,
The charged dust particles are collected on the dust collecting electrode by the electrostatic force between the dust collecting electrode plate and the non-dust collecting electrode plate.

The operation of the piezoelectric high-voltage power supply 1 of the first embodiment configured as described above will be described below.

For example, when the load 2 of 6 MΩ is connected to the device 1, the output voltage detection circuit 16 of the output value detection circuit section 7 detects the detection output voltage VK obtained by dividing the output voltage Vi from the rectification circuit 6. And outputs it to the control circuit 8.

The output current detection circuit 16 detects a current I flowing when the output voltage Vi is applied to the load 2, and outputs the output current value VA to the control circuit section 8.

The magnitude judging circuit 20 of the control circuit section 8 compares the detected output voltage VK with the detected current value VA. If the detected current value VA is larger, the constant current control circuit 22 is operated to maintain a constant value. A current output (for example, 1 mA) is obtained.

When the detected output voltage VK is higher, the constant voltage control circuit 21 is operated to obtain a constant output voltage (for example, 6 kV).

For example, when the constant voltage control circuit 21 operates, the constant voltage control circuit 21 determines the resistance value (aΩ) of the resistor R10 and the resistance value (bΩ) of the resistor R12 as shown in FIG. ), The output characteristic has a slope determined by the following equation: output VOPV = b / a (V base V−detection output voltage V
K) For example, a V group V; 6 V (corresponding to 6 kV) VK; 7 V is obtained.

Therefore, the output VFV of the constant voltage control circuit 21
Is determined by the resistors R14, R15, R16 and the power supply voltage, so that VFV = 12− (12−VOPV) D / (C + D).

That is, the result is as shown in FIG.

This output VFV is sent to the VF conversion circuit 23. As shown in FIG. 11C, the VF conversion circuit 23 has a relationship in which the gate control signal frequency fg is determined by the input voltage VFV. When the voltage VFV is low, the frequency fg decreases, and the voltage VFV increases. If it is high, the frequency fg increases. That is, as shown in FIG. 11D, the VF conversion circuit 23 has a curve (curve shown on the lower side) in which, for example, the oscillation frequency fg10 when VFV = 10 V is an output voltage Vi = 6 kV in a standard state. What needs to be achieved is that Vi = 7 due to load fluctuation (fluctuation in resistance, etc.) due to disturbance or the like.
Assuming that the curve is kV (the curve shown on the upper side), the output voltage is set to a value fgv subtracted from the oscillation frequency fg10 in order to obtain a constant output voltage as described above. 6 kV is obtained.

On the other hand, when the constant current control circuit 22 operates, the slope has a slope determined by the resistance value (EΩ) of the resistor R20 and the resistance value (FΩ) of the resistor R22, as shown in FIG. Because of the output characteristics, the output V _opI = F / E (detection current VA−V base I) For example, V base I; 6 V (corresponding to 1 mA) is obtained.

Therefore, the output VFI of the constant current control circuit 22
Is determined by the resistors R24, R25, R26 and the power supply voltage, so that VFI = 12− (12−V _opI ) H / (G + H).

That is, the result is as shown in FIG.

The output VFI is sent to the VF conversion circuit 23. In the VF conversion circuit 23, as shown in FIG. 12C, the gate control signal frequency fg is determined by the input voltage VFI. When the power VFI is low, the frequency fg decreases and the voltage VFI increases. And the frequency fg increases. That is, as shown in (d) of FIG. 12, the VF conversion circuit 23 has a curve (curve shown on the lower side) in which, for example, the oscillation frequency fg6 when VFI = 6 V is an output current I = 1000 μA in a standard state. What is to be achieved is I = 12 due to load fluctuations (fluctuations in resistance, etc.) due to disturbances, etc.
Assuming that the curve has a value of 00 μA (curve shown on the upper side), the oscillation current fg6 is increased from the oscillation frequency fg6 in order to obtain the constant output current as described above, and the output current has a constant value, that is, I = Try to get 1000 μA.

Accordingly, when such a gate control signal F having the frequency fg is input to the gate of the power MOSFET Q1, the constants of the components of the resonance circuit 10 of the piezoelectric transformer are, in the present embodiment, inductance L2 = 801 [μH] C2 + C3 = 5.47 [nF] fg = 85.12 [kHz], and for L1 C1, L1> 2
[ΜH] and C1 were 3 [nF] <C1 <15
As shown in FIG. 13, constant frequency or constant current control is performed at a boundary between the resonance frequency when the frequency f is 6 MΩ and a load line (reference impedance 6 MΩ) as shown in FIG. Become. FIG. 13 shows that when the frequency f increases, the output voltage increases, and when the frequency f is 6 MΩ or less, the output current decreases.

<Second Embodiment> FIG. 14 is a schematic configuration diagram of a second embodiment. The piezoelectric high-voltage power supply 30 according to the second embodiment directly inputs a power supply voltage to the control circuit 31,
By outputting a gate control signal fg having a frequency corresponding to the voltage fluctuation to the power MOSFET Q1, a constant output can be obtained in response to a temperature change or the like with a simple configuration.

As shown in FIG. 15, the control circuit 31 includes resistors R36 to R43, capacitors C4, C5, C
P9, diodes D7, D8, D9, D10, transistors Q6, Q7, NAND1, 2 and so on. The power supply voltage is input to CP9, resistor R40, the collector of transistor Q6, and the power supply of NAND1, and the duty ratio is 1: 1.
The gate control signal F whose frequency corresponds to the fluctuation of the power supply voltage
Generate

That is, as shown in FIG. 16, when the output voltage becomes equal to or less than the reference voltage VDD (dotted line), the output voltage sharply drops to perform a constant current control operation. Unlike the first embodiment, a constant voltage control circuit and a constant current control circuit are not required.

<Third Embodiment> FIG. 17 is a schematic diagram of a third embodiment. In the third embodiment, the output of the constant voltage control circuit 21 is provided with a limit circuit 35 including zener diodes DZ1 and DZ2 so that the frequency of the output from the constant voltage control circuit 21 falls within a certain range at the time of disturbance or rising. Even when the upper and lower limits are set by the Zener diodes DZ1 and DZ2, the output is suppressed within a certain range even when the values deviate from the range, thereby controlling the frequency fluctuation of the VF conversion unit to be constant.

A timer or the like is connected to the constant voltage control circuit 21 and a bypass circuit (not shown) for bypassing the limit circuit 35 is provided. Of the gate control signal from the VF conversion circuit to be stabilized at a constant level, and thereafter, the use of the limit circuit 35 is released, and the constant voltage is normally used by using the bypass circuit. The output of the control circuit 21 may be sent to the VF conversion circuit.

In the third embodiment, the output of the constant voltage control circuit 21 is provided with the limit circuit 35. However, the output of the constant current control circuit 22 may be provided with the limit circuit 35.

[0075]

As described above, according to the present invention, the resonance inductance connected to the drive electrode of the piezoelectric transformer,
A resonance capacitance connected in parallel to the piezoelectric transformer and a phase fine adjustment for connecting the switching element in parallel so that the phase of the sine wave applied to the piezoelectric transformer matches the phase of the control signal to the switching element. A frequency of a sine wave to the piezoelectric transformer is determined by a resonance circuit including capacitance.

For this reason, the sine wave distortion to the drive electrode of the piezoelectric transformer can be easily adjusted by the fine adjustment capacitance with a simple configuration, and a nearly perfect sine wave can always be applied to the piezoelectric transformer. Thus, even if the load fluctuates, the conversion efficiency can be maintained at a high efficiency equal to or higher than a certain level.

That is, there is an effect that a constant output can be obtained even with a change in load with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a piezoelectric high-voltage power supply device according to a first embodiment.

FIG. 2 is a characteristic diagram of an ideal piezoelectric high-voltage power supply device according to the present embodiment.

FIG. 3 is an explanatory diagram illustrating characteristics of the resonance circuit according to the first embodiment.

FIG. 4 is a schematic configuration diagram of an output value detection circuit and a control circuit according to the first embodiment.

FIG. 5 is an explanatory diagram illustrating switching due to a load change.

FIG. 6 is a schematic configuration diagram of a constant voltage control circuit.

FIG. 7 is an explanatory diagram illustrating characteristics of a constant voltage control circuit.

FIG. 8 is an explanatory diagram illustrating characteristics of a constant current control circuit.

FIG. 9 is an explanatory diagram illustrating characteristics of a constant current control circuit.

FIG. 10 is a schematic configuration diagram of a VF conversion circuit according to the first embodiment.

FIG. 11 is an operation explanatory diagram when a constant voltage control circuit is selected.

FIG. 12 is an operation explanatory diagram when a constant current control circuit is selected.

FIG. 13 is an explanatory diagram illustrating an output characteristic due to a frequency change.

FIG. 14 is a schematic configuration diagram of a piezoelectric high-voltage power supply device according to a second embodiment.

FIG. 15 is a schematic configuration diagram of a VF conversion circuit according to a second embodiment.

FIG. 16 is an explanatory diagram illustrating an effect when the VF conversion circuit according to the second embodiment is used.

FIG. 17 is a schematic configuration diagram of a piezoelectric high-voltage power supply device according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric high voltage power supply 2 Load (air purifier) 5 DC power supply L1 Inductance Q1 Power MOSFET L2 Inductance C2 Capacitance C1 Capacitance C3 Piezoelectric transformer 8 Control circuit part 7 Output value detection circuit part 10 Resonance circuit 16 Output voltage detection circuit

Claims (9)

[Claims] An inductor and a switching element are connected in series to a DC power supply, and the switching element is turned on and off to apply a sine wave of a predetermined frequency to a driving electrode of the piezoelectric transformer to obtain an output terminal of the piezoelectric transformer. A high-voltage output obtained by rectifying and amplifying an output signal to be applied to a load, wherein one of the switching elements is connected to the driving element of the piezoelectric transformer, and the other is connected to a driving electrode of the piezoelectric transformer. A capacitance for phase fine adjustment, which is connected in parallel and fine-tunes the phase of the sine wave so that the phase of the sine wave applied to the piezoelectric transformer matches the phase of the gate control signal to the switching element; A piezoelectric high-voltage power supply device comprising a connected resonance capacitance. . 2. The switching device according to claim 1, wherein the switching element has a control circuit for generating a gate control signal having a predetermined duty ratio for increasing the conversion efficiency of the piezoelectric transformer. Piezoelectric high voltage power supply. 3. The control circuit according to claim 2, wherein the resonance frequency exceeds 1 based on a resonance frequency based on the resonance inductance, the resonance capacitance, and the capacitance of the piezoelectric transformer.
2. The gate control signal having a frequency of less than 1.2 is sent to the switching element.
Or the piezoelectric high-voltage power supply device according to 2. 4. The control circuit is connected to an output value detection circuit that detects a voltage and a current of the high-voltage output when the load is connected to an output terminal of the rectifier circuit. A determination is made as to whether the state of the load is in a constant voltage region or a constant current region based on a detected voltage and a detected current value. 4. The drive output of claim 1, wherein the drive output is obtained as the high voltage output.
The piezoelectric high-voltage power supply according to the above description. 5. The control circuit, when judging that the current is in the constant voltage area or the constant current area, changes a frequency with respect to a reference frequency for obtaining a reference output voltage or a reference output current from the detection voltage or the detection current. 2. The method according to claim 1, wherein the gate control signal having the frequency of the generated signal is generated and output.
The piezoelectric high-voltage power supply device according to 2, 3, or 4. 6. The control circuit according to claim 1, wherein the control circuit includes a limiter for suppressing the frequency change within a predetermined range during a period when the resonance circuit rises. 6. The piezoelectric high-voltage power supply device according to 5. 7. The piezoelectric high-voltage power supply device according to claim 1, wherein said control circuit does not use said limit means after said rise time. 8. The piezoelectric high-voltage power supply device according to claim 1, further comprising a second control circuit that changes the frequency of the gate control signal based on a power supply voltage, instead of the control circuit. 9. The apparatus according to claim 1, wherein the load is an electrode of an electrostatic precipitator.
Or the piezoelectric high-voltage power supply device according to 8.