JP2001054280A - Power supply device with piezoelectric transformer and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency, stabilize output, and expand a control range by maintaining drive frequency near a fluctuating resonance frequency with a simple configuration, even if the resonance frequency fluctuates due to the fluctuation of a load and the temperature of a piezoelectric transformer in a power supply device having the piezoelectric transformer that is used for consumer equipment and industrial equipment. SOLUTION: A resonance frequency, corresponding to the output of a piezoelectric transformer 3 being actually detected, can be evaluated from the relationship between the resonance frequency and output of the piezoelectric transformer 3 under fluctuations of a load or the like. An area near the resonance frequency, evaluated according to the output of the piezoelectric transformer 3, is set to the variable limit of the frequency of the output of a drive means in frequency control, or is set to the frequency of the output of the drive means in control other than the frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stabilized DC power supply or inverter used in consumer or industrial equipment, which has a piezoelectric transformer.

[0002]

2. Description of the Related Art In a conventional power control method having a piezoelectric transformer, as described below, the drive frequency is changed by utilizing the relationship between the output near the resonance frequency of the piezoelectric transformer and the drive frequency. There was something to make.

FIGS. 14 and 15 are examples of circuit diagrams showing the output control by the frequency of the output of the conventional driving means. A DC power supply 1 obtained by rectifying and smoothing a DC power supply or a commercial AC power supply supplies a voltage to the driving means 2 of the piezoelectric transformer 3. The driving means 2 drives the piezoelectric transformer 3 with an output having a frequency corresponding to the output of the frequency control means 7. At this time, the frequency (drive frequency) of the vibration actually generated in the piezoelectric transformer 3 becomes substantially equal to the output frequency of the drive means 2. The output of the piezoelectric transformer 3 is converted into direct current by the rectifying and smoothing means 4 in FIG. 14, and then directly sent to the load 6 in FIG. The output detection means 5 monitors the output of the piezoelectric transformer 3 sent to the load 6. The frequency control means 7 controls the frequency of the output of the driving means 2 according to the output of the output detection means 5.

FIG. 18 shows the relationship between the output voltage of the piezoelectric transformer 3 (more precisely, the boost ratio which is the ratio of the input voltage to the input voltage), the efficiency, and the drive frequency. Peak position f of a curve representing the relationship between output voltage and drive frequency (hereinafter referred to as frequency characteristic curve)
₀ is the resonance frequency of the piezoelectric transformer 3. As shown in FIG. 18, the efficiency of the piezoelectric transformer 3 is highest near the resonance frequency. Therefore, it is necessary to control the driving frequency within this range.

The control of the driving frequency is specifically as follows.
Had been done. As an example, the circumference as shown in FIG.
The output voltage of a piezoelectric transformer having wave number characteristics
Is stabilized to a predetermined target value V.
No fluctuation of load etc., that is, resonance frequency f₀Is constant
And the peak P of the frequency characteristic curve₀
(Driving frequency is resonance frequency f₀And the output at that time
Voltage is V₀Control point).
Target point P to be determined₁(The driving frequency is f₁At that time
The point at which the input voltage is V)
It is assumed that the distance is sufficiently larger than the magnitude of the voltage fluctuation.
If the output voltage fluctuates from the target value V, output to the target value V
To return the voltage, set the drive frequency to the target value f₁Change up to
It should be done. To change the driving frequency,
What is necessary is just to change the frequency of the output of 2. Where the target value V
The output of drive means 2 is determined by the sign of the difference between
Is increased or decreased. In the example of FIG.
Drive frequency f at which voltage becomes V₁Adjust the drive frequency to
In the direction of the arrow on the curve,
Is increased or decreased. The direction of this arrow is the output voltage target value V.
It depends on the height. For example, as shown in FIG.₁
From the point P to the point P, that is, the driving frequency is f₁Yo
F when the output voltage becomes v lower than V
Frequency control means 7 reduces the frequency of the output of drive means 2
Let it. Then, the driving frequency f decreases in the direction of the arrow on the point P.
The output voltage v slightly increases toward V. Point P is controlled
Target point P₁Peak P against₀Closer to
Dynamic frequency is f ₁When the output voltage is smaller than V
Is also controlled by the point P₁I was able to return to.
By controlling the drive frequency as described above, the output to the load 6
Could be stabilized to a predetermined target value V.

[0006] Next, a conventional output control method in a power supply device having a piezoelectric transformer includes the following.
Drive means 2 near the efficient resonance frequency of the piezoelectric transformer
Drive frequency, phase, etc.
In some cases, the output was controlled by components other than the output frequency of 2.

FIGS. 16 and 17 are examples of circuit diagrams showing conventional output control by phase. DC power supply obtained by rectifying and smoothing DC power supply or commercial AC power supply
1 supplies a voltage to the driving means 2 of the piezoelectric transformer 3. The drive unit 2 drives the piezoelectric transformer 3 according to the output of the phase control unit 10. In FIG. 16, the output of the piezoelectric transformer 3 is converted into direct current by the rectifying / smoothing means 4 and then sent directly to the load 6 in FIG. Output detection means 5 is load 6
Monitor the output sent to. The phase control means 10 controls the phase of the output of the driving means 2 according to the output of the output detection means 5. By controlling the phase, the drive frequency of the piezoelectric transformer 3 is controlled, and the output to the load 6 is stabilized at a predetermined level.

[0008]

However, the power supply device having the above-described conventional piezoelectric transformer has the following problems. First, the problem in the case where control is performed according to frequency will be described. The shape of the frequency characteristic curve of the piezoelectric transformer 3 varies as shown by curves A to E in FIG. 19 depending on the state of the load (for example, the resistance value). In particular, the peak position of the frequency characteristic curve fluctuates along the curve F in FIG. That is, the resonance frequency f ₀ is varied. Further, as shown in FIG. 20, the resonance frequency also changes due to the temperature change of the piezoelectric transformer. On the other hand, in the conventional frequency control, as described above, after ignoring the fluctuation of the resonance frequency, as shown in FIG. 21A, the peak P ₀ of the frequency characteristic curve and the control target point P _{1 correspond} to the drive frequency. And that the distance is sufficiently larger than the magnitude of the output fluctuation. Therefore, if the resonance frequency fluctuates so much as to override this premise, the above-mentioned control cannot be established as follows.

For example, as shown in FIG.
(Peak P)₀)
(Peak P₀'), That is, the resonance frequency is f
₀To f ₀Suppose that it fluctuates to '. Predetermined output voltage
Control method used to maintain the control target value V
Is driven by the difference between the output voltage and the control target value V.
The frequency is increased or decreased. That is, the arrow on the curve of FIG.
The drive frequency changes in the direction of the mark. Fig. 21
Unlike Fig. 21 (a), peak P in Fig. 21 (b)₀'And control target point P₁'When
The driving frequency is peak P₀', And even eyes
Mark P₁Point P having the same output voltage value V as₂'Beyond
Can move. If it reaches point P '' in FIG. 21 (b), then
Output voltage drops below the target value V.
According to the control method, the output frequency of the driving means is further reduced
Will be. As a result, the driving frequency is also on point P ''
It decreases further in the direction of the arrow. As a result, the voltage deviates from V
Output voltage fluctuated in the direction of Also, fluctuation
Output voltage at the specified resonance frequency is lower than the control target value V
The output voltage will continue to decrease.
Had been.

In order to solve this problem, conventionally, for example, the lower limit of the output frequency of the driving means is fixed to a value higher than the expected fluctuation range of the resonance frequency, or the output is controlled to a predetermined target value. In the case where the driving frequency cannot be obtained, a method of sweeping the driving frequency again from a sufficiently high side has been adopted (Japanese Patent Laid-Open No. 8-107678). When the lower limit value for the output frequency of the driving means is fixed, it is necessary to set the lower limit value to a value higher than an expected fluctuation range of the resonance frequency due to the load fluctuation.
However, such a setting is disadvantageous because driving near the resonance frequency is desirable from the viewpoint of good efficiency. In addition, re-sweeping of the driving frequency causes a temporary decrease in output to the load, which may have an adverse effect on the load side.

Next, in the case of the output control by the phase, there is a problem that the efficiency is reduced as shown in FIG. 18 when the resonance frequency is shifted from the vicinity of the driving frequency due to the fluctuation of the load. In order to solve this problem, there has been proposed a power supply device having a piezoelectric transformer provided with a resonance frequency detection circuit and a resonance frequency tracking circuit for adjusting the drive frequency to the fluctuated resonance frequency. However, there is a problem that the circuit is complicated or the resonance frequency cannot be detected if the drive waveform is distorted. It is an object of the present invention to solve the above problems, that is, to perform output control with a simple circuit that can maintain high-efficiency drive regardless of the load or the temperature of the piezoelectric transformer.

[0012]

In order to solve the above-mentioned problems, a power supply apparatus having a piezoelectric transformer for controlling frequency according to the present invention comprises a piezoelectric transformer, a drive for driving the piezoelectric transformer by an output having a predetermined frequency. Means, an output detecting means for detecting an output from the piezoelectric transformer to a load, and a frequency of an output of the driving means in a range not exceeding a predetermined variable limit in accordance with an output of the piezoelectric transformer detected by the output detecting means. Frequency control means for controlling the output of the piezoelectric transformer so as to maintain the output of the piezoelectric transformer at a predetermined magnitude, and the piezoelectric detection means detected by the output detection means from the relationship between the resonance frequency and the output of the piezoelectric transformer in a load change. Frequency variable limit setting means for load fluctuation, setting a variable limit for the frequency of the output of the driving means according to the output of the transformer Having.

Thus, for example, when the drive frequency fluctuates beyond the point P ₂ ′ in FIG. 21 (b), the frequency control means further reduces the output frequency of the drive means and further increases the output from the control target value. A variable limit can be set for the frequency of the output of the driving means so as not to move away. This variable limit is set according to the output of the piezoelectric transformer from the relationship between the resonance frequency and the output of the piezoelectric transformer in the case of a load change as shown by the curve F in FIG. Specifically, it is set as follows according to the type of output of the piezoelectric transformer to be detected. For example, consider the case where the drive frequency is controlled by detecting the output voltage of a piezoelectric transformer.
Assume that the state of the piezoelectric transformer corresponds to the point a in FIG. That is, the output voltage is v, and the drive frequency is f. First, a frequency f 'at a point b on the curve F corresponding to the output voltage v is obtained. A variable limit for the output frequency of the driving means at the output voltage v is set near f '.
Thereafter, in order to increase the output voltage v to the target value V, the drive frequency f is reduced by the above-described conventional control method. At this time, each time the output voltage v changes with the change of the drive frequency f, the variable limit f 'for the output voltage is reset. Here, the variable limit f 'is always set near the curve F, as is clear from the above-described method of determining the variable limit. Then, as the drive frequency f decreases, the variable limit f ′ increases. The driving frequency f varies beyond the control target point P _1, when it reaches to a peak P _0, the variable limit f 'also peaks P _0. That is, the drive frequency f and the variable limit f 'match at the resonance frequency f _0. At this point, the conventional control is stopped, and the output frequency of the driving means is fixed, for example, to the value at that time. Therefore, the driving frequency f does not continue to decrease and stops at the point where the resonance frequency is not exceeded. As a result,
Unlike the conventional case, the output voltage does not depart from the control target value V. The above effects are the same even when the drive frequency is controlled by detecting the output current of the piezoelectric transformer.

Consider a case where the output voltage and the output current of the piezoelectric transformer are detected and controlled. For example, when the load resistance is calculated, the changed resonance frequency can be obtained from the relationship between the load resistance and the resonance frequency as shown in FIG. The obtained resonance frequency is set as a variable limit for the output frequency of the driving means. Then, similarly to the case where the output voltage is detected and controlled as described above, even if the driving frequency is about to decrease beyond the fluctuated resonance frequency, the output frequency of the driving means stops at the resonance frequency, so that the driving The frequency does not drop below the resonance frequency. As described above, even if the resonance frequency fluctuates, the variable limit can be set so that the drive frequency can be controlled in the vicinity thereof. Further, the set value can be estimated only from the output of the piezoelectric transformer at an arbitrary driving frequency without searching for the changed resonance frequency by re-sweeping the driving frequency.

Further, the power supply apparatus having a piezoelectric transformer for performing frequency control according to the present invention is a temperature detector for detecting the temperature of the piezoelectric transformer, and a temperature detector for outputting an output corresponding to the detected temperature of the temperature detector. Means, and the frequency variable limit setting means for the load change may set the variable limit, assuming that the temperature of the piezoelectric transformer is a temperature corresponding to the output of the temperature detecting means. As a result, as a result of the fluctuation of the temperature of the piezoelectric transformer, for example, in the case of detecting the output voltage described above, even if the curve representing the relationship between the resonance frequency and the output of the piezoelectric transformer like the curve F in FIG. 19 fluctuates. The vicinity of the fluctuated curve becomes the variable limit of the drive frequency. In addition, when detecting the load resistance, in addition to the relationship between the frequency characteristics of the piezoelectric transformer and the load resistance as shown in FIG. 19, the relationship between the temperature and the resonance frequency of the piezoelectric transformer as shown in FIG. The obtained resonance frequency can be set as a variable limit. Therefore, even if the load or temperature fluctuates, the drive frequency does not change beyond the vicinity of the resonance frequency.

Further, the power supply device having a piezoelectric transformer for performing frequency control according to the present invention is a piezoelectric transformer, a driving means for driving the piezoelectric transformer with an output having a predetermined frequency, and an output detecting means for detecting the output of the piezoelectric transformer. ,
In accordance with the output of the piezoelectric transformer detected by the output detecting means, the output frequency of the driving means is changed within a range not exceeding a predetermined variable limit so as to maintain the output of the piezoelectric transformer at a predetermined magnitude. Frequency control means for controlling, a temperature detector for detecting the temperature of the piezoelectric transformer, temperature detecting means for outputting in accordance with the detected temperature of the temperature detector, and when the temperature fluctuation of the piezoelectric transformer is within a predetermined range. A frequency variable limit setting means for setting a variable limit with respect to a frequency of an output of the driving means near a resonance frequency of the piezoelectric transformer at a temperature of the piezoelectric transformer corresponding to an output of the temperature detecting means. .

Thus, even if the temperature of the piezoelectric transformer fluctuates, the temperature can be detected, and the resonance frequency at the detected temperature can be determined from the relationship between the temperature of the piezoelectric transformer and the resonance frequency as shown in FIG. Therefore, the vicinity of the resonance frequency at the detected temperature after the fluctuation can be set as the variable limit of the drive frequency. For this reason, the driving frequency of the piezoelectric transformer does not change beyond the vicinity of the resonance frequency due to the temperature fluctuation.

Next, in order to solve the above-mentioned problems, a power supply device having a piezoelectric transformer for performing control other than the frequency according to the present invention includes a piezoelectric transformer, a driving unit for driving the piezoelectric transformer with an output having a predetermined frequency, Output detection means for detecting the output from the piezoelectric transformer to the load, according to the output of the piezoelectric transformer detected by the output detection means,
Control means for controlling a component other than the frequency of the output of the driving means to maintain the output of the piezoelectric transformer at a predetermined level; and a relationship between the resonance frequency and the output of the piezoelectric transformer in a load change. A frequency setting means for setting a frequency of an output of the driving means in accordance with an output of the piezoelectric transformer detected by the output detection means.

Thus, the resonance frequency corresponding to the output of the piezoelectric transformer detected by the output detecting means is obtained from the relationship between the resonance frequency and the output of the piezoelectric transformer as shown by a curve F in FIG. The drive frequency is set. Therefore, even if the resonance frequency fluctuates due to load fluctuation,
The driving frequency does not significantly deviate from the vicinity of the resonance frequency.

The frequency setting means for this load change is
For example, when detecting the output voltage of a piezoelectric transformer,
A circuit with input / output characteristics approximating the relationship between the resonance frequency of the piezoelectric transformer and the output voltage as shown by the curve F in 19,
Further, the detection of the load resistance can be realized by providing circuits having input / output characteristics approximating the relationship between the load resistance and the resonance frequency obtained from FIG. The construction of these circuits is relatively simpler than conventional ones. However, in these circuits, the output voltage or the load resistance corresponds to the output of the output detecting means input to the frequency setting means for the load change, and the resonance frequency corresponds to the output from the frequency setting means to the drive means for the load change. Let it.

Further, according to the present invention, a power supply device having a piezoelectric transformer for controlling a frequency other than the frequency is a temperature detector for detecting the temperature of the piezoelectric transformer, and performs an output corresponding to the detected temperature of the temperature detector. Temperature detecting means,
Assuming that the temperature of the piezoelectric transformer is a temperature corresponding to the output of the temperature detecting means, the frequency setting means for the load change may set the frequency of the output of the driving means. With this configuration, even if the curve F in FIG. 19 fluctuates due to fluctuations in the temperature of the piezoelectric transformer, the drive frequency is set near the fluctuated curve F. Therefore, even if the load or the temperature fluctuates, the driving frequency does not largely deviate from the vicinity of the resonance frequency.

Further, according to the present invention, there is provided a power supply device having a piezoelectric transformer for performing control other than the frequency, a piezoelectric transformer, a driving means for driving the piezoelectric transformer by an output having a predetermined frequency, and an output for detecting the output of the piezoelectric transformer. Control for controlling the output of the piezoelectric transformer to be maintained at a predetermined level by changing a component other than the frequency of the output of the driving unit in accordance with the output of the piezoelectric transformer detected by the output detecting unit; Means, a temperature detector for detecting the temperature of the piezoelectric transformer, a temperature detecting means for performing an output corresponding to the detected temperature of the temperature detector, and the temperature at the temperature of the piezoelectric transformer corresponding to the output of the temperature detecting means. A frequency setting unit for setting a frequency of an output of the driving unit near a resonance frequency of the piezoelectric transformer;

Thus, even if the temperature of the piezoelectric transformer fluctuates, the temperature can be detected. For example, the resonance frequency at the detected temperature can be determined from the relationship between the temperature of the piezoelectric transformer and the resonance frequency as shown in FIG. Therefore, the drive frequency can be set near the resonance frequency at the detected temperature after the change.
As a result, the drive frequency does not largely deviate from the vicinity of the resonance frequency due to the temperature fluctuation.

The frequency setting means for this temperature fluctuation is:
This can be realized by having a circuit having input / output characteristics approximating the relationship between the temperature and the resonance frequency of the piezoelectric transformer as shown by the curve in FIG. 20, so that the circuit is relatively simpler than the conventional one.
Here, in FIG. 20, the temperature of the piezoelectric transformer corresponds to the output of the temperature detecting means input to the frequency setting means for temperature fluctuation, and the resonance frequency corresponds to the output from the frequency setting means to the driving means for temperature fluctuation. Let it.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to FIGS. 1 to 13, FIGS. 18 to 20, and FIG. << Embodiment 1 >> FIG. 1 is a configuration diagram showing Embodiment 1. still,
The same components as in FIG. 14 which is a conventional example are denoted by the same reference numerals, and description thereof will be omitted. Frequency variable limit setting means 8a for load fluctuation, the variable limit of the frequency output from the frequency control means 7, according to the output of the output detection means 5,
Set as in the following specific example. Thus, when the output to the load is controlled to a predetermined value, the frequency of the output of the driving means 2 does not change beyond the resonance frequency even if the load fluctuates.

FIG. 2 shows a preferred specific example of the frequency control means 7 and the frequency variable limit setting means 8a for load fluctuation in the first embodiment. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. Output detecting unit 5 includes a rectifier output voltage or output current of the smoothing means 4 detects the output voltage v _i corresponding to the voltage or current
Set. Frequency control means 7 includes an operational amplifier A2, a resistor A
3, a circuit A composed of A4, A5, a capacitor A6, and a DC power supply A7, a diode A1, and a voltage controlled oscillator (VCO) 7
a. Voltage V of the circuit A input voltage v _i and the DC power supply A7
comparing the _a, increases or decreases the output voltage v _a in proportion to the difference. Here, to assume the output voltage v _i of the output detecting means 5 when the output of the voltage transformer 3 is a control target value, the voltage V _a is set. The VCO 7a determines the frequency of the output to the driving means 2 according to the input voltage v. The driving means 2 determines the frequency of the output to the piezoelectric transformer according to the frequency of the output of the VCO 7a. The piezoelectric transformer 3 vibrates at a drive frequency equal to the output frequency of the drive means 2.

From the above configuration, the drive frequency corresponds to the input voltage v of the VCO 7a. Further, in a conventional manner the output voltage v _i of the output and the output detecting unit 5 of the piezoelectric transformer 3 corresponds. From the above correspondence, the frequency characteristic curve of the piezoelectric transformer 3 (when the detected output of the piezoelectric transformer 3 is, for example, a voltage, the curve in FIG. 18 is a typical example) is converted to the VCO input voltage v.
When redrawn into a curve representing the relationship between the output voltage V _i and the output voltage vi of the output detection means 5, the curve shown in FIG. As described below with reference to the curve of the FIG. 23 (a), the by input-output characteristics of the circuit A, so that the output voltage v _i of the output detection means 5 is equal to the voltage V _a of the DC power supply A7, Drive means 2 by VCO 7a
The output frequency is controlled.

Initially, the driving frequency of the piezoelectric transformer 3 is initialized.
Resonance frequency f₀(Fig. 18)
If you set it higher. VCO input voltage v
_aIn the initial state, for example, the peak position of the curve in FIG.
Place v_PHigher than. Circuit A input voltage v_iIs the voltage V_aHigher
Circuit A is the output voltage v to VCO7a_aIncrease and vice versa
To voltage v_iIs the voltage V_aIf lower, the voltage v _aDecrease
You. Therefore, the voltage v is applied to the VCO 7a._aWhen you enter, Figure 23 (a)
Voltage v in the direction of the arrow on the curve_aChanges. this
Result, voltage v_aIs v_i= V_aInput voltage of VCO7a corresponding to
Pressure value v_a0It is kept close. This means that the drive frequency
The frequency at which the output of the piezoelectric transformer 3 matches the control target
It means that it is kept near the numerical value.

Frequency variable limit setting means for load fluctuation
8a includes a circuit B including an operational amplifier B2, resistors B3 and B4, and a DC power supply B5, and a diode B1. Circuit B
Is configured for example, the output voltage v _b to VCO7a is a linear function of the input voltage v _i. This linear function is determined as follows. For example, when the output voltage of the piezoelectric transformer 3 is detected, as shown by the curve F in FIG. 19, the resonance frequency f ₀ fluctuated due to the fluctuation of the load 6 is changed when the driving frequency is equal to the resonance frequency f _0. 3 as a function of the output voltage v ₀ . The output voltage of the output detection means 5 corresponding to the voltage v ₀ is defined as _vi . And
From the expression of the resonance frequency f ₀ as a function of the voltage v ₀ ,
v determine the resonance frequency at the time of ₀ = v _i. The input voltage of VCO7a corresponding to equal the driving frequency to the value of the resonant frequency and v _b. Then, a function (curve F in FIG. 19) showing the resonance frequency f ₀ by a voltage v _0, functions representing the voltage v _b at a voltage v _i (curve in FIG. 23 F ') and correspond. In particular, when the fluctuation range of the load 6 is sufficiently small, this function is approximated by a linear function. That is, the voltage v _b is a linear function of the voltage v _i. Therefore, determining the function representing the output voltage v _b of the circuit B in the input voltage v _i to match the linear function. Even when the output current of the piezoelectric transformer 3 is detected, when the relationship between the resonance frequency corresponding to the curve F in FIG. 19 and the output current can be approximated by a linear function, the input / output characteristics of the circuit B can be similarly determined.

If the input / output characteristics of the circuit B are determined in this way, even if the load fluctuates, in the case of the above-described control, for example, the frequency of the output of the driving means 2 becomes lower than the resonance frequency as follows. Not be. As shown in FIG.
A case where the control target point P ₁ from the peak P ₀ of the frequency characteristic curve is sufficiently far away than the size of the variation in the output or the like of the piezoelectric transformer 3, a point corresponding to the actual driving state of the piezoelectric transformer 3 It has never reaches a peak P ₀ is a variation of the output or the like. The output voltage v _a of for circuit A circuit B
_Is always higher than the output voltage vb. At this time, diode A
1 conducts, the diode B1 has lost continuity, the output voltage v _a of the circuit A is input to VCO7a, the above control is performed.

When the resonance frequency fluctuates due to load fluctuation,
Correspondingly, the curve in FIG. 23 (a) changes to the curve (solid line) in FIG. 23 (b) (the broken line curve in FIG. 23 (b) is the curve in FIG. 23 (a) before the change). Represents). And the peak P of the curve
The distance between _{0 'and} the control target point P _1' is assumed that closer than the magnitude of the fluctuations in the output or the like of the piezoelectric transformer 3. At this time, if the fluctuating drive frequency attempts to lower beyond the resonance frequency, that is, if the voltage v _a lowers beyond the peak position v _P , the operating point a reaches the peak P ₀ ′ and the circuit B The point “b” representing the state also reaches the peak P ₀ ′. At this point, the magnitude relationship between the output voltage v _b of the output voltage v _a and the circuit B of the circuit A is reversed to the boundary peak position v _P.
At the time of this reversal, the diode A1 loses conduction, and the control of the output frequency of the driving means 2 by the operation of the circuit A as described above stops. On the other hand, the conducting diode B1 are simultaneously state where the input voltage v of VCO7a matches the output voltage v _b of the circuit B, that, is a state corresponding on the curve F 'shown in FIG. 23 (b) is maintained. Therefore, the state where the output frequency of the driving means 2 matches the resonance frequency (on the curve F in FIG. 19) is maintained, and the driving frequency does not become lower than the resonance frequency. When the voltage v _a becomes larger than the voltage v _b again, the above-described control is restarted.

In the first embodiment, the fluctuation range of the load 6 is sufficiently small.
Finally, the resonance frequency f₀The voltage v ₀Function for (Figure
The 19 curves F) were approximated by a linear function. And against it
Corresponding voltage v_bThe voltage v_i, The circuit B
The input / output characteristic (curve F ′ in FIG. 23) was defined as a linear function. Only
And a function that approximates the actual function form
May be used. Then, the frequency of the output of the driving means 2
No longer changes beyond the resonance frequency.
You. Also, depending on the type of output of the pressure transformer 3 to be detected.
Therefore, the output detection means 5 is in parallel with the
May be.

Embodiment 2 FIG. 3 is a configuration diagram showing Embodiment 2. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In the first embodiment, the output of the rectifying / smoothing means 4 is detected by the output detection means 5. However, loads such as cold-cathode tubes can be used without rectification. Therefore, in the second embodiment, the output of the piezoelectric transformer 3 is directly detected by the output detection means 5 with the configuration shown in FIG. Thus, even if the rectifying and smoothing means 4 is omitted, the frequency of the output of the driving means 2 does not change beyond the resonance frequency even if the load fluctuates, just like the first embodiment. Therefore, the driving frequency does not greatly deviate from the vicinity of the resonance frequency.
Note that a rectifying and smoothing means may be provided between the output detection means 5 and the load 6. This is because as long as the output detection means 5 directly detects the output of the piezoelectric transformer 3, the operation of the present invention does not change.

Embodiment 3 FIG. 4 is a configuration diagram showing Embodiment 3. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof will be omitted. The temperature detector 9a detects the temperature of the piezoelectric transformer 3. The temperature detecting means 9 sends an output corresponding to the temperature detected by the temperature detector 9a to the frequency variable limit setting means 8b for temperature fluctuation. The frequency variable limit setting means 8b for the temperature fluctuation is controlled by the following frequency control means so that the frequency of the output of the driving means 2 does not change beyond the resonance frequency even if the resonance frequency fluctuates due to the temperature fluctuation.
7 sets a variable limit for the output frequency of the driving means 2 to be changed.

For example, the frequency variable limit setting means 8b for temperature fluctuation has the same configuration as the circuit B of the first embodiment. Here, as the input / output characteristics of the configuration, those obtained by approximating the curve in FIG. 20 are used. However, the resonance frequency f ₀ and the output correspond to each other, and the temperature of the piezoelectric transformer 3 and the output of the temperature detecting means 9 correspond to each other. Thus, the first embodiment
Similarly, the resonance frequency fluctuated due to temperature fluctuation and the driving means 2
When the frequency of the output of the
Control stops. Then, the situation is maintained until the drive frequency deviates from the resonance frequency to a controllable direction. As a result, even if the temperature fluctuates, the driving frequency does not largely deviate from the vicinity of the resonance frequency.

Embodiment 4 FIG. 5 is a configuration diagram showing Embodiment 4. 5, the same components as those in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. In the third embodiment, the output of the rectifying / smoothing means 4 is detected by the output detection means 5. In the fourth embodiment, the output of the piezoelectric transformer 3 is directly detected by the output detection unit 5 with the configuration shown in FIG. Accordingly, even when the rectifying and smoothing means 4 is omitted, the driving frequency does not largely deviate from the vicinity of the resonance frequency even when the temperature fluctuates, similarly to the third embodiment. Note that a rectifying and smoothing means may be provided between the output detection means 5 and the load 6. This is because as long as the output detection means 5 directly detects the output of the piezoelectric transformer 3, the operation of the present invention does not change.

<< Embodiment 5 >> FIG. 6 is a block diagram showing a fifth embodiment. 6, the same components as those in FIG. 1 or FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. The frequency variable limit setting means 8a for the load fluctuation includes the output detecting means 5
, As well as from the temperature detecting means 9. With this configuration, with respect to load fluctuation, as in the first embodiment,
The frequency variable limit setting means 8a for the load fluctuation controls the frequency control means 7. Further, when the temperature of the piezoelectric transformer 3 fluctuates, the frequency variable limit setting means 8a for load fluctuations
The curve at the temperature of the piezoelectric transformer 3 corresponding to the output of the temperature detecting means 9 is selected as the curve F in FIG. As a result, even if the load or the temperature fluctuates, the driving frequency does not largely deviate from the vicinity of the resonance frequency.

Embodiment 6 FIG. 7 is a block diagram showing Embodiment 6. 7, the same components as those in FIG. 6 are denoted by the same reference numerals, and description thereof will be omitted. In the fifth embodiment, the output of the rectifying / smoothing means 4 is detected by the output detection means 5. In the sixth embodiment, the output of the piezoelectric transformer 3 is directly detected by the output detection means 5 with the configuration shown in FIG. Thus, even if the rectifying and smoothing means 4 is omitted, the driving frequency does not largely deviate from the vicinity of the resonance frequency even when the load or the temperature fluctuates, just like the fifth embodiment. Note that a rectifying and smoothing means may be provided between the output detection means 5 and the load 6. This is because as long as the output detection means 5 directly detects the output of the piezoelectric transformer 3, the operation of the present invention does not change.

Embodiment 7 FIG. 8 is a configuration diagram showing Embodiment 7. 8, the same components as those in FIG. 16 are denoted by the same reference numerals, and description thereof will be omitted. When the load variation is within a predetermined range, the frequency setting means 11a for the load variation is such that the drive frequency is maintained near the resonance frequency.
In accordance with the output of the output detecting means 5, the following control for the driving means 2 is performed. Frequency setting means 11 for load fluctuation
a is a piezoelectric track, for example, as in the circuit B of the first embodiment.
When detecting the output voltage of No. 3, it has a configuration having input / output characteristics approximating the curve F of FIG. As shown in the first embodiment, this can be realized with a circuit that is relatively simple as compared with the related art.

With this configuration, even if the resonance frequency fluctuates due to the load fluctuation, the resonance frequency fluctuated from the output of the output detecting means at the time of the fluctuation can be evaluated. If the driving unit 2 is controlled so that the output frequency is adjusted to a value near the evaluated value, the driving frequency is maintained near the resonance frequency. Therefore, the driving frequency can be kept close to the resonance frequency with a relatively simple circuit even if the load fluctuates.

<< Eighth Embodiment >> FIG. 9 is a configuration diagram showing an eighth embodiment. 9, the same components as those of FIG. 8 are denoted by the same reference numerals, and the description thereof will be omitted. In the seventh embodiment, the output of the rectifying / smoothing means 4 is detected by the output detection means 5. In the eighth embodiment, the output of the piezoelectric transformer 3 is directly detected by the output detection means 5 with the configuration shown in FIG. Thus, even if the rectifying / smoothing means 4 is omitted, the driving frequency is maintained near the resonance frequency even when the load fluctuates, just like the seventh embodiment. Note that a rectifying and smoothing means may be provided between the output detection means 5 and the load 6. This is because as long as the output detection means 5 directly detects the output of the piezoelectric transformer 3, the operation of the present invention does not change.

Embodiment 9 FIG. 10 is a configuration diagram showing Embodiment 9. 10, the same components as those in FIG. 4 or FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted. The frequency setting means 11b for the temperature fluctuation controls the driving means 2 as described below so that the driving frequency is kept close to the resonance frequency even if the resonance frequency fluctuates due to the temperature fluctuation. For example, the frequency setting means 11b for the temperature fluctuation is the circuit B of the first embodiment.
It has the same configuration as Here, as the input / output characteristics of the configuration, those obtained by approximating the curve in FIG. 20 are used. However,
The resonance frequency f ₀ and the output correspond to each other, and the temperature of the piezoelectric transformer 3 and the output of the temperature detecting means 9 correspond to each other.

Thus, similarly to the seventh embodiment, even if the resonance frequency fluctuates due to temperature fluctuation, the value can be evaluated. If the driving means 2 is controlled so that the output frequency is adjusted to this evaluation value, the driving frequency is maintained near the resonance frequency. As in the seventh embodiment, the frequency setting means 11b for this temperature fluctuation
Can be realized with a simpler circuit than before. Therefore, the driving frequency can be kept close to the resonance frequency even if the temperature fluctuates, with a relatively simple circuit.

<< Embodiment 10 >> FIG. 11 is a block diagram showing a tenth embodiment. 11, the same components as those in FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. In the ninth embodiment, the output of the rectifying / smoothing means 4 is detected by the output detection means 5. In the tenth embodiment, the piezoelectric transformer 3 has a configuration as shown in FIG.
Is directly detected by the output detection means 5. This allows
Even if the rectifying / smoothing means 4 is omitted, the driving frequency is kept close to the resonance frequency even when the load fluctuates, just like the ninth embodiment. Note that a rectifying and smoothing means may be provided between the output detection means 5 and the load 6.

<< Embodiment 11 >> FIG. 12 is a block diagram showing Embodiment 11. 12, the same components as those in FIG. 8 or FIG. 10 are denoted by the same reference numerals, and description thereof will be omitted. The frequency setting means 11a for the load fluctuation is input not only from the output detection means 5 but also from the temperature detection means 9. With this configuration, the frequency setting unit 11a for the load change controls the driving unit 2 for the load change as in the seventh embodiment. Further, when the temperature of the piezoelectric transformer 3 fluctuates, the frequency setting means 11a with respect to load fluctuation approximates the input / output characteristics as a curve F in FIG. 19 at the temperature of the piezoelectric transformer 3 corresponding to the output of the temperature detecting means 9. Is selected. As a result, even if the load or the temperature fluctuates, the drive frequency is kept near the resonance frequency.

<Twelfth Embodiment> FIG. 13 is a structural diagram showing a twelfth embodiment. 13, the same components as those in FIG. 12 are denoted by the same reference numerals, and description thereof will be omitted. In the eleventh embodiment, the output of the rectifying / smoothing means 4 is detected by the output detection means 5. In the twelfth embodiment, a piezoelectric transformer
The output 3 is directly detected by the output detection means 5. This allows
Excluding the rectifying / smoothing means 4, exactly the same as in the eleventh embodiment,
Even if the load or the temperature fluctuates, the drive frequency is kept near the resonance frequency. Note that a rectifying and smoothing means may be provided between the output detection means 5 and the load 6.

Of the above embodiments, the embodiments 1, 2, 5,
In 8, 11, and 12, the output detection means 5 is independent of the one that outputs to the frequency control means 7 or the phase control means 10 and the one to the frequency variable limit setting means 8a or the frequency setting means 11a for load fluctuation. May exist. At this time, the type of output detected by each output detecting unit may be either or both of the output voltage and the output current, or may be either the load resistance or the output power. Further, the types of outputs to be detected may be different.

In the first to sixth embodiments, the frequency control means 7
May perform complex control with other than frequency, such as phase and input voltage. Examples 3 to 6
And 9 to 12, the temperature detector 9a includes a thermistor,
A thermocouple, a phototransistor for measuring infrared radiation temperature, a photodiode, or the like may be used as long as its output correlates with the temperature of the piezoelectric transformer.

[0049]

As described above, in the power supply device having the piezoelectric transformer of the present invention, first, as for the power supply device for controlling the frequency, the driving means 2 is provided with a relatively simple structure against load or temperature fluctuations. Can be prevented from changing over the fluctuated resonance frequency. Therefore, even if the load or the temperature fluctuates, the drive frequency can be stably controlled without being largely deviated from the vicinity of the resonance frequency. As a result, the piezoelectric transformer can be driven with high efficiency. Further, since the variable limit of the frequency of the output of the driving means 2 can be reset in accordance with the output of the piezoelectric transformer, the range of the load fluctuation in which the output can be stabilized becomes wider than before.

Next, the power supply device having the piezoelectric transformer of the present invention that performs control other than the frequency has a relatively simple configuration, and has a resonance circuit in which the frequency of the output of the driving means 2 fluctuates even if the load or the temperature fluctuates. It can be kept near the frequency. Therefore, the driving frequency does not deviate significantly from the vicinity of the fluctuated resonance frequency. Therefore, the piezoelectric transformer can be driven with high efficiency even if the load or the temperature fluctuates.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a first embodiment of the present invention.

FIG. 2 is a specific configuration diagram of Embodiment 1 of the present invention.

FIG. 3 is a configuration diagram illustrating a second embodiment of the present invention.

FIG. 4 is a configuration diagram illustrating a third embodiment of the present invention.

FIG. 5 is a configuration diagram illustrating a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram illustrating a fifth embodiment of the present invention.

FIG. 7 is a configuration diagram illustrating a sixth embodiment of the present invention.

FIG. 8 is a configuration diagram illustrating a seventh embodiment of the present invention.

FIG. 9 is a configuration diagram illustrating an eighth embodiment of the present invention.

FIG. 10 is a configuration diagram illustrating a ninth embodiment of the present invention.

FIG. 11 is a configuration diagram illustrating a tenth embodiment of the present invention.

FIG. 12 is a configuration diagram illustrating an eleventh embodiment of the present invention.

FIG. 13 is a configuration diagram illustrating a twelfth embodiment of the present invention.

FIG. 14 is a configuration diagram showing a conventional example for performing frequency control.

FIG. 15 is a configuration diagram showing a conventional example in which frequency control is performed and the output is AC.

FIG. 16 is a configuration diagram showing a conventional example for performing phase control.

FIG. 17 is a configuration diagram showing a conventional example in which phase control is performed and the output is AC.

FIG. 18 is a diagram illustrating a typical relationship between a driving frequency, an output voltage, and efficiency.

FIG. 19 is a diagram illustrating a typical change in the shape of a frequency characteristic curve due to a load change.

FIG. 20 is a diagram illustrating a typical variation of a resonance frequency due to a temperature variation.

FIG. 21 is a diagram showing a method of controlling an output voltage by a driving frequency.

FIG. 22 is a diagram illustrating a setting method of a variable limit of a driving frequency based on a curve F representing a resonance frequency variation.

FIG. 23 is a diagram illustrating a frequency characteristic curve in a relationship between a VCO input voltage and an output of an output detection unit.

[Explanation of symbols]

1 DC power supply with rectified and smoothed DC power supply or commercial AC power supply 8a Frequency variable limit setting means for load fluctuation 8b Frequency variable limit setting means for temperature fluctuation 11a Frequency setting means for load fluctuation 11b Frequency setting means for temperature fluctuation

Claims (17)

[Claims] A piezoelectric transformer, a driving unit for driving the piezoelectric transformer with an output having a predetermined frequency, an output detecting unit for detecting an output from the piezoelectric transformer to a load, and a driving unit for the piezoelectric transformer detected by the output detecting unit. Frequency control means for changing the frequency of the output of the driving means within a range not exceeding a predetermined variable limit in accordance with the output so as to control the output of the piezoelectric transformer to a predetermined magnitude; and From the relationship between the resonance frequency and the output of the piezoelectric transformer, a variable limit for the frequency of the output of the driving unit is set according to the output of the piezoelectric transformer detected by the output detecting unit. A power supply device having a piezoelectric transformer, characterized by having means. 2. A piezoelectric transformer, a driving unit for driving the piezoelectric transformer by an output having a predetermined frequency, an output detecting unit for detecting an output from the piezoelectric transformer to a load, and a driving unit for the piezoelectric transformer detected by the output detecting unit. Frequency control means for controlling the output of the piezoelectric transformer to maintain a predetermined magnitude by changing the frequency of the output of the driving means within a range not exceeding a predetermined variable limit in accordance with the output; A temperature detector for detecting a temperature of the piezoelectric transformer corresponding to an output of the temperature detector, and driving the piezoelectric transformer near a resonance frequency of the piezoelectric transformer at a temperature of the piezoelectric transformer corresponding to an output of the temperature detector. Setting a variable limit for the frequency of the output of the means,
A power supply device having a piezoelectric transformer, comprising frequency variable limit setting means for temperature fluctuation. 3. A temperature detector for detecting a temperature of the piezoelectric transformer, and a temperature detector for performing an output according to a temperature detected by the temperature detector, wherein the temperature of the piezoelectric transformer is the temperature detector. 2. A power supply device having a piezoelectric transformer according to claim 1, wherein the frequency variable limit setting means for the load fluctuation sets the variable limit assuming that the temperature corresponds to the output of the piezoelectric transformer. 4. A piezoelectric transformer, a driving unit for driving the piezoelectric transformer with an output having a predetermined frequency, an output detecting unit for detecting an output from the piezoelectric transformer to a load, a driving unit for the piezoelectric transformer detected by the output detecting unit. Control means for controlling a component other than the frequency of the output of the driving means in accordance with the output to maintain the output of the piezoelectric transformer at a predetermined magnitude; and a resonance frequency of the piezoelectric transformer in a load change. A frequency setting unit for setting a frequency of an output of the driving unit in accordance with an output of the piezoelectric transformer detected by the output detection unit from a relationship between the output and the output. Power supply having. 5. A piezoelectric transformer, a driving unit for driving the piezoelectric transformer with an output having a predetermined frequency, an output detecting unit for detecting an output from the piezoelectric transformer to a load, a driving unit for the piezoelectric transformer detected by the output detecting unit. Control means for controlling a component other than the frequency of the output of the driving means in accordance with the output to maintain the output of the piezoelectric transformer at a predetermined magnitude; a temperature detector for detecting the temperature of the piezoelectric transformer A temperature detecting means for performing an output corresponding to a temperature detected by the temperature detector; and an output of the driving means near a resonance frequency of the piezoelectric transformer at a temperature of the piezoelectric transformer corresponding to an output of the temperature detecting means. A power supply device having a piezoelectric transformer, comprising frequency setting means for setting a frequency and for temperature fluctuation. 6. A temperature detector for detecting a temperature of the piezoelectric transformer, and a temperature detector for outputting the temperature in accordance with a temperature detected by the temperature detector, wherein the temperature of the piezoelectric transformer is the temperature of the temperature detector. The power supply device having a piezoelectric transformer according to claim 4, wherein the frequency setting means for the load fluctuation sets the frequency of the output of the driving means assuming that the temperature corresponds to the output. 7. The piezoelectric device according to claim 1, further comprising rectifying and smoothing means for rectifying and smoothing the output of the piezoelectric transformer, and through which the output detecting means detects the output of the piezoelectric transformer. A power supply device having a transformer. 8. The apparatus according to claim 1, wherein said output detecting means detects an output current of said piezoelectric transformer.
A power supply device having the piezoelectric transformer according to claim 1. 9. The apparatus according to claim 1, wherein said output detecting means detects an output voltage of said piezoelectric transformer.
A power supply device having the piezoelectric transformer according to claim 1. 10. A power supply device having a piezoelectric transformer according to claim 1, wherein said output detecting means detects both an output current and an output voltage of said piezoelectric transformer. 11. The output detecting means detects a resistance of a load or an output power.
A power supply device having the piezoelectric transformer according to claim 1. 12. The piezoelectric transformer is driven by an input having a predetermined frequency, and an output from the driven piezoelectric transformer to a load is directly output.
Alternatively, a variable limit for the frequency of the input of the piezoelectric transformer is set in accordance with the detected output of the piezoelectric transformer from the relationship between the resonance frequency and the output of the piezoelectric transformer in a load change, which is detected after rectification and smoothing. The frequency of the input of the piezoelectric transformer changes in response to the detected output of the piezoelectric transformer, and if the changed frequency does not exceed the variable limit, the frequency also exceeds the variable limit. If the variable limit is set as the frequency of the input of the piezoelectric transformer,
An output control method for a piezoelectric transformer, wherein the output of the piezoelectric transformer is controlled to be maintained at a predetermined level. 13. A piezoelectric transformer is driven by an input having a predetermined frequency, and an output from the driven piezoelectric transformer to a load is directly output.
Alternatively, the temperature of the piezoelectric transformer is detected after rectification and smoothing, and the variable limit for the frequency of the input of the piezoelectric transformer is set near the resonance frequency of the piezoelectric transformer at the detected temperature of the piezoelectric transformer. The frequency of the input of the piezoelectric transformer changes according to the detected output of the piezoelectric transformer, and if the changed frequency does not exceed the variable limit, the frequency also exceeds the variable limit. An output control method for a piezoelectric transformer, wherein the variable limit is set as an input frequency of the piezoelectric transformer, so that the output of the piezoelectric transformer is controlled to be maintained at a predetermined magnitude. 14. The temperature of the piezoelectric transformer is detected, and the variable limit is set as the temperature of the piezoelectric transformer is the detected temperature.
An output control method of the piezoelectric transformer described in the above. 15. A piezoelectric transformer is driven by an input having a predetermined frequency, and an output from the driven piezoelectric transformer to a load is directly outputted.
Alternatively, the frequency of the input of the piezoelectric transformer is set in accordance with the detected output of the piezoelectric transformer from the relationship between the resonance frequency and the output of the piezoelectric transformer in a load change, which is detected after rectification and smoothing. According to the output of the piezoelectric transformer, components other than the frequency of the input of the piezoelectric transformer change,
An output control method for a piezoelectric transformer, wherein the output of the piezoelectric transformer is controlled to be maintained at a predetermined level. 16. A piezoelectric transformer is driven by an input having a predetermined frequency, and an output from the driven piezoelectric transformer to a load is directly output.
Alternatively, the temperature of the piezoelectric transformer is detected after rectification and smoothing, the temperature of the piezoelectric transformer is detected, and the input frequency of the piezoelectric transformer is set near the resonance frequency of the piezoelectric transformer at the detected temperature of the piezoelectric transformer. According to the output of the piezoelectric transformer, components other than the frequency of the input of the piezoelectric transformer change,
An output control method for a piezoelectric transformer, wherein the output of the piezoelectric transformer is controlled to be maintained at a predetermined level. 17. The piezoelectric device according to claim 15, wherein a temperature of the piezoelectric transformer is detected, and an input frequency of the piezoelectric transformer is set assuming that the temperature of the piezoelectric transformer is the detected temperature. Transformer control method.