JPH10174436A - Piezoelectric element drive circuit - Google Patents

Piezoelectric element drive circuit

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Publication number
JPH10174436A
JPH10174436A JP34659196A JP34659196A JPH10174436A JP H10174436 A JPH10174436 A JP H10174436A JP 34659196 A JP34659196 A JP 34659196A JP 34659196 A JP34659196 A JP 34659196A JP H10174436 A JPH10174436 A JP H10174436A
Authority
JP
Japan
Prior art keywords
piezoelectric
reactance
load
impedance
circuit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
JP34659196A
Other languages
Japanese (ja)
Inventor
Norio Matsumoto
規雄 松本
Original Assignee
Mitsui Chem Inc
三井化学株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsui Chem Inc, 三井化学株式会社 filed Critical Mitsui Chem Inc
Priority to JP34659196A priority Critical patent/JPH10174436A/en
Publication of JPH10174436A publication Critical patent/JPH10174436A/en
Withdrawn legal-status Critical Current

Links

Abstract

(57) [Problem] To provide a piezoelectric element drive circuit capable of supplying a large amount of electric power at a low voltage at a low cost. A primary terminal of a piezoelectric transformer is provided.
, An inductance element 60 is connected in parallel with the piezoelectric transformer 10, and a capacitance element 50 is connected in series with the piezoelectric transformer 10 between the primary terminal 31 and the terminal 33. An AC power supply 40 is connected between terminals 33 and 34. By the inductance element 60 and the capacitance element 50, the real number component of the impedance Z seen from the power supply 40 as viewed from the inductance element 60, the capacitance element 50, the piezoelectric transformer 10, and the load 45 is converted into primary terminals 31 and 32.
Therefore, the impedance is made smaller than the real component of the impedance as viewed from the piezoelectric transformer 10 and the load 45 so that a large power can be supplied to the load 45 with a lower input voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric element driving circuit, and more particularly to a piezoelectric transformer driving circuit.

[0002]

2. Description of the Related Art In recent years, a piezoelectric element has been used as a power transmission element such as a piezoelectric transformer or a powerful ultrasonic transducer. In mobile devices, high-efficiency piezoelectric elements have been adopted to reduce power consumption. Since a portable device is driven by a battery, the driving voltage of the piezoelectric element is limited by the battery voltage. Therefore, a piezoelectric element capable of supplying a large amount of electric power at a low voltage and a driving circuit thereof are desired.

As a countermeasure, a method of reducing the input impedance of the piezoelectric element itself by forming the piezoelectric element in a laminated structure, and a method of providing an electromagnetic transformer for boosting in front of the piezoelectric element have been adopted.

[0004]

However, in order to manufacture a piezoelectric element having a laminated structure, there is a problem that the manufacturing process is complicated and the manufacturing cost of the piezoelectric element is increased.
Also, a method in which an electromagnetic transformer for boosting is provided in a preceding stage,
There is a problem that the cost increases.

Accordingly, it is an object of the present invention to provide a piezoelectric element drive circuit which can supply a large amount of electric power at a low voltage while suppressing cost.

Another object of the present invention is to provide a piezoelectric element driving circuit which can improve the power factor and reduce the load on active elements such as driving transistors.

It is still another object of the present invention to provide a piezoelectric element drive circuit with a variable boost ratio.

[0008]

Means for Solving the Problems To achieve the above object, the present inventors have conducted intensive studies and found that instead of providing a step-up electromagnetic transformer in front of a piezoelectric element, a simple external inductance element was used. And using a capacitance element,
An alternative to the boost effect of the conventional electromagnetic transformer has been obtained.

That is, when a conventional step-up electromagnetic transformer is used, a combined load resistance composed of a piezoelectric element such as a piezoelectric transformer or an ultrasonic transducer and a load is regarded as a pure resistance and the winding ratio of the electromagnetic transformer is determined. I was trying to boost. However, a piezoelectric element such as a piezoelectric transformer or an ultrasonic transducer is not a pure resistance but a composite reactance resistance. Therefore, the combined load resistance including the piezoelectric element and the load is not a pure resistance but a composite reactance resistance. If this is the case, the impedance is controlled using a reactance element such as an external inductance element or capacitance element, and the external component from the power supply is smaller than the real component of the impedance when the load is viewed from the electric input terminal of the piezoelectric element. The real component of the impedance when viewing a circuit including a reactance element, a piezoelectric element, and a load can be reduced, and in this way, the boost ratio can be increased without using an electromagnetic transformer. However, when such an external reactance element is used, the impedance has a frequency dependence. However, a piezoelectric element such as a piezoelectric transformer or an ultrasonic transducer uses its resonance characteristics, so that a wide frequency range is considered. It is not necessary that the impedance be controlled as described above by an external reactance element at the resonance frequency.

Further, the impedance is controlled by using an external reactance element, and a real number component of impedance when a load is viewed from an electric input terminal of the piezoelectric element is compared with an external reactance element and a piezoelectric element from a power supply. The real component of the impedance when a circuit including a load is viewed can be made different. In this way, the step-up ratio can be made variable by an external reactance element.

Further, an imaginary component (reactance component) of impedance when a load is viewed from an electric input terminal of the piezoelectric element using an external reactance element is removed,
The reactance component of the impedance when viewing a circuit including an external reactance element, a piezoelectric element, and a load from the power supply can be reduced to almost zero. In this way, the power factor is improved, and the driving transistor is improved. Thus, the burden on the active element can be reduced. On the other hand, in the method in which the step-up electromagnetic transformer is provided in the preceding stage, the power factor of the piezoelectric element is not improved, so that there is a problem that a load on an active element such as a driving transistor increases.

Next, the concept underlying the present invention will be further described with reference to FIGS.

A power conversion circuit 100 using the piezoelectric element 10
Can be generally represented as shown in FIG.

On the other hand, the power conservation law is "the sum of the effective power of the power supply is equal to the sum of the power consumed by the resistance elements". Therefore, if the drive circuit 20 and the piezoelectric element 10 are ideal and have no loss, , The effective power (supply power) of the AC power supply is completely consumed by the load resistor 45. That is,

[0015]

(Equation 1) Here, Re represents a real number component.

On the other hand, considering the impedance Z (see FIG. 2) as viewed from the power supply,

[0017]

(Equation 2)

Substituting equation (2) into equation (1),

[0019]

(Equation 3)

In general,

## EQU4 ## Z = R + jX (4) From the viewpoint of power supply efficiency,

It is preferable that X = 0 (5).

Therefore, now

X = 0 (6)

## EQU7 ## Assuming that Z = R (7), equation (3) becomes

P L = | Ei | 2 / R (8)

That is, in order to supply the electric power P L to the load resistance R L , the driving circuit 20 satisfies the following equation (9).
May be used.

[0023]

R = Ei 2 / P L (9) (where,

Ei 2 = | Ei | 2 (10) )

With reference to the circuit diagram of FIG. 3, the concept underlying the present invention will be described more specifically.

FIG. 3 is a circuit diagram for explaining a specific example of the piezoelectric element driving circuit according to the present invention. In this piezoelectric element drive circuit, a reactance element 82 is provided between a primary terminal 31 connected to the primary electrode 11 of the piezoelectric transformer 10 and a primary terminal 32 connected to the primary electrode 12 of the piezoelectric transformer 10. (JA) is connected in parallel to the piezoelectric transformer 10, a reactance element 81 (jB) is connected in series to the piezoelectric transformer 10 between the primary terminal 31 and the terminal 33, and one end of the load 45 is connected to the piezoelectric transformer 10. The other end of the load 45 is connected to the secondary electrode 13 of the transformer 10 and the primary electrode 12 and the primary terminal 3 of the piezoelectric transformer 10 are connected to each other.
2 and the terminal 34 are connected in common,
Are connected between the terminals 33 and 34.

In this circuit, the reactance element 8
2 (jA), the real component Re (Z) of the impedance Z can be adjusted when the reactance elements 81 and 82, the piezoelectric transformer 10 and the load 45 are viewed from the terminals 33 and 34.
The imaginary component Im (Z) of the impedance Z can be adjusted by the reactance element 81 (jB).

The impedance Z is determined by the primary terminal 3
Assuming that the impedance of the piezoelectric transformer 10 and the load 45 from 1, 32 is Zpt,

[Mathematical formula-see original document] Z = jB + [1 / {(1 / jA) + (1 / Zpt)}] (11)

## EQU12 ## When expressed as Z = R + jX (12), theoretically,

X = O (13) At that time, the supply power P is given by

P = V 2 / R (14)

Therefore, when it is desired to supply the electric power P to the load 45,

R = V 2 / P (15)

In the circuit of FIG. 3, if the impedance when the load 45 is viewed from the primary side terminal pairs 31 and 32 of the piezoelectric transformer 10 is (r-jx),

R = A 2 r / (A 2 + r 2 + x 2 -2Ax) (16) X = {A (r 2 + x 2 -Ax) / (A 2 + r 2 + x 2 -2Ax)} + B (17)

A is obtained from equation (16). A> 0 is an inductance, and A <0 is a capacitance.

Then, B is obtained from equation (17). B
> 0 is inductance, and B <0 is capacitance. When B = 0, the reactance element 81 (jB) becomes unnecessary.

The reactance element 8 determined in this way
If 2 (jA) and 81 (jB) are used, the power factor can be improved by setting the reactance component of the impedance Z to zero, and desired power can be supplied to the load 45 at a desired input voltage.

As described above, according to the piezoelectric element drive circuit 112 illustrated in FIG. 3, the real component Re () of the input impedance Z of the piezoelectric transformer 10 is controlled by the reactance element 82 (jA) connected in parallel to the piezoelectric transformer 10. Z), and the imaginary component Im (Z) of the input impedance can be eliminated by the reactance element 81 (jB) connected in series to the piezoelectric transformer 10, so that the impedance Z seen from the power supply circuit 40 can be adjusted to a desired value. Can be set to a value. The reactance element 81 (j
Since B) and 82 (jA) are ideally lossless, the loss of the drive circuit 112 is not ideal. On the other hand, the real component Re (Z) of the impedance Z consumes power, but since the loss of the piezoelectric transformer 10 is ideally zero, all the power consumption is supplied to the load 45. This power is (power supply voltage V) 2 / (impedance Z
Of the impedance Z, the desired power can be adjusted by adjusting the real component Re (Z) of the impedance Z.
5 can be supplied. When it is desired to supply a large power at a low power supply voltage, the real number component Re of the impedance Z is obtained.
What is necessary is just to set (Z) to a small value.

The piezoelectric element driving circuit 11 shown in FIG.
2, as described above, the reactance element 82
(JA) and 81 (jB), the terminal 3
The real component Re (Z) of the impedance Z as viewed from the reactance elements 81 and 82, the piezoelectric transformer 10 and the load 45 from the terminals 3 and 34, and the real component Re of the impedance Zpt from the piezoelectric terminals 10 and the load 45 viewed from the primary terminals 31 and 32. (Zpt), but as shown in FIG. 4, a series inductance element 81 ′ (jB ′) is replaced with a parallel inductance element 82 (jA) and a piezoelectric transformer 1.
0 and the primary electrode 11, the reactance elements 82 (jA) and 81 ′ (jB ′) are added, and the reactance elements 81 ′ and 8
2. The real number component Re (Z) of the impedance Z as viewed from the piezoelectric transformer 10 and the load 45 is converted to the primary terminals 31, 32.
Thus, the real component Re (Zpt) of the impedance Zpt as seen from the piezoelectric transformer 10 and the load 45 can be made larger.

The present invention has been made based on such findings. According to claim 1, a piezoelectric element, a load connected to the piezoelectric element, and a power supply for driving the piezoelectric element and the load are provided. In the piezoelectric element driving circuit provided, by electrically connecting one or more reactance elements in series and / or in parallel to the electric input terminal of the piezoelectric element, the driving frequency of the piezoelectric element at the driving frequency of the piezoelectric element Than the real component of the first impedance when the load is viewed from the electrical input terminal, the second when the circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from the power supply. A piezoelectric element drive circuit is provided, wherein the real component of impedance is reduced.

According to a second aspect of the present invention, in a piezoelectric element driving circuit including a piezoelectric element and a power supply for driving the piezoelectric element and a load to be connected to the piezoelectric element, an electric input terminal of the piezoelectric element Electrically connecting one or more reactance elements in series and / or in parallel to form a first impedance when the load is viewed from the electric input terminal of the piezoelectric element at a driving frequency of the piezoelectric element. The real component of the second impedance when the circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from the power supply is smaller than the real component of A piezoelectric element drive circuit is provided.

According to the piezoelectric element driving circuit of the first or second aspect, the input impedance of the piezoelectric element itself is reduced by forming the piezoelectric element in a laminated structure, or a step-up electromagnetic transformer is provided in front of the piezoelectric element. Even if not, one or more reactance elements electrically connected in series and / or parallel to the electric input terminal of the piezoelectric element can provide a piezoelectric element drive circuit with an increased step-up ratio. Thus, a piezoelectric element drive circuit capable of supplying a large amount of power can be provided at low cost.

Further, according to the third aspect, by connecting the one or more reactance elements, the driving frequency of the piezoelectric element when the load is viewed from the electric input terminal of the piezoelectric element at the drive frequency of the piezoelectric element. The imaginary component of the impedance of 1 is almost canceled, and the imaginary component of the second impedance when the circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from the power supply is set to substantially zero. A piezoelectric element drive circuit according to claim 1 or 2 is provided.

In this way, the power factor is improved, and the load on the active element such as a driving transistor can be reduced.

According to a fourth aspect of the present invention, the absolute value of the imaginary part of the second impedance is set to 0.2 or less of the absolute value of the second impedance. A piezoelectric element drive circuit is provided.

In this way, the power factor becomes 98% or more (corresponding to a phase shift of ± 15 ° or less). The second
If the absolute value of the imaginary part of the impedance exceeds 0.2 times the absolute value of the second impedance, the efficiency of the power supply decreases, which is not preferable. More preferably, the absolute value of the imaginary part of the second impedance is set to 0.087 or less of the absolute value of the second impedance.
In this case, the power factor is more preferably 99.6% or more (corresponding to a phase shift of ± 5 ° or less).

According to claim 5, the one or more reactance elements electrically connected in series and / or parallel to the electric input terminal of the piezoelectric element are connected to the electric input terminal of the piezoelectric element. A first reactance element electrically connected in parallel to the piezoelectric element, and a second reactance element electrically connected in series to the electric input terminal of the piezoelectric element. 4. A piezoelectric element drive circuit according to any one of the above items 4.

According to a sixth aspect of the present invention, there is provided the piezoelectric element driving circuit according to the fifth aspect, wherein the first reactance element is an inductance element, and the second reactance element is a capacitance element. Provided.

According to a seventh aspect of the present invention, there is provided the piezoelectric element driving circuit according to the fifth aspect, wherein the first reactance element is a capacitance element, and the second reactance element is an inductance element. Provided.

The first reactance element electrically connected in parallel to the electric input terminal of the piezoelectric element has a higher withstand voltage than the second reactance element electrically connected in series to the electric input terminal of the piezoelectric element. Is required, and in general, the withstand voltage of the inductance element is higher than that of the capacitance element. Therefore, the withstand voltage of the piezoelectric element drive circuit according to claim 6 is higher than the withstand voltage of the piezoelectric element drive circuit according to claim 7. Things are obtained.

According to a twelfth aspect of the present invention, there is provided the piezoelectric element driving circuit according to the first aspect, wherein the piezoelectric element is a piezoelectric transformer.

According to a ninth aspect, there is provided the piezoelectric element driving circuit according to any one of the first to eighth aspects, wherein the load is a cold cathode tube.

According to a tenth aspect, there is provided a liquid crystal display device incorporating the piezoelectric element driving circuit according to the first aspect.

According to an eleventh aspect, there is provided an electronic device incorporating the piezoelectric element driving circuit according to the first aspect.

According to a twelfth aspect, the piezoelectric element driving circuit according to any one of the first to seventh aspects is provided, wherein the piezoelectric element is an ultrasonic transducer.

According to the thirteenth aspect, the piezoelectric element includes:
In a piezoelectric element driving circuit including a load connected to the piezoelectric element, and a power supply for driving the piezoelectric element and the load, one circuit is electrically connected to an electric input terminal of the piezoelectric element in series and / or parallel. By connecting the above reactance element, at the drive frequency of the piezoelectric element, the real component of the first impedance when the load is viewed from the electric input terminal of the piezoelectric element is compared with the one component from the power supply. A piezoelectric element drive circuit is provided, wherein the real component of the second impedance is different when looking at the circuit including the reactance element, the piezoelectric element, and the load.

According to a fourteenth aspect, in a piezoelectric element driving circuit including a piezoelectric element and a power supply for driving the piezoelectric element and a load to be connected to the piezoelectric element, an electric input terminal of the piezoelectric element By electrically connecting one or more reactance elements in series and / or in parallel, at a driving frequency of the piezoelectric element, the first impedance of the first impedance when the load is viewed from the electric input terminal of the piezoelectric element. A piezoelectric element, wherein a real component of a second impedance is different from a real component when a circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from the power supply. A drive circuit is provided.

According to the piezoelectric element driving circuit of the thirteenth or fourteenth aspect, the electric input terminal of the piezoelectric element has:
By one or more reactance elements electrically connected in series and / or in parallel, a piezoelectric element drive circuit with a variable step-up ratio can be obtained. As a result, a piezoelectric element drive circuit with a variable step-up ratio can be provided at low cost. it can.

According to the fifteenth aspect, by connecting the one or more reactance elements, the driving frequency of the piezoelectric element at the drive frequency when the load is viewed from the electric input terminal of the piezoelectric element is determined. The imaginary component of the impedance of 1 is almost canceled, and the imaginary component of the second impedance when the circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from the power supply is set to substantially zero. A piezoelectric element drive circuit according to claim 1 or 2 is provided.

Further, according to claim 16, a piezoelectric element,
In a piezoelectric element driving circuit including a load connected to the piezoelectric element, and a power supply for driving the piezoelectric element and the load, one circuit is electrically connected to an electric input terminal of the piezoelectric element in series and / or parallel. By connecting the reactance element described above, at the drive frequency of the piezoelectric element, the reactance component of the first impedance when the load is viewed from the electric input terminal of the piezoelectric element is removed, and the one-to-one power supply is connected to the power supply. A piezoelectric element drive circuit is provided, wherein the reactance component of the second impedance is substantially zero when a circuit including one or more reactance elements, the piezoelectric element, and the load is viewed.

According to the seventeenth aspect, the piezoelectric element includes:
In a piezoelectric element driving circuit comprising a power supply for driving a load to be connected to the piezoelectric element and the piezoelectric element,
An electrical input terminal of the piezoelectric element is electrically connected in series and / or
Or by connecting one or more reactance elements in parallel, at the drive frequency of the piezoelectric element, to remove the reactance component of the first impedance when viewing the load from the electric input terminal of the piezoelectric element,
A piezoelectric element drive circuit is provided, wherein a reactance component of a second impedance when the circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from the power source is substantially zero. You.

According to the piezoelectric element driving circuit of the present invention, the power factor can be improved and the load on the active element such as a driving transistor can be reduced.

According to claim 18, the piezoelectric element drive circuit according to any one of claims 13 to 17, wherein the piezoelectric element is a piezoelectric transformer.

[0059]

Next, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 5 is a circuit diagram for explaining a piezoelectric transformer driving circuit according to a first embodiment of the present invention, and FIG. 6 is a piezoelectric transformer for comparison. FIG. 3 is a circuit diagram for explaining the drive circuit of FIG.

In the piezoelectric element driving circuit 122 of the first embodiment, the primary electrode 11 of the piezoelectric transformer 10
The inductance element 60 (Lp) is connected between the primary terminal 31 connected to the primary side terminal 32 and the primary side terminal 32 connected to the primary side electrode 12 of the piezoelectric transformer 10.
, A capacitance element 50 (Cs) is connected in series with the piezoelectric transformer 10 between the primary terminal 31 and the terminal 33, and one end of a load 45 (RL) is connected to the two ends of the piezoelectric transformer 10. The other end of the load 45 (RL) is connected to the primary electrode 12, the primary terminal 32, and the terminal 34 of the piezoelectric transformer 10 in common, and the AC power supply 40 (Vin). Are connected between the terminals 33 and 34.

It is assumed that 1 W of power is supplied from a power supply voltage of 5 V to a load resistor 45 (RL) of 100 kΩ.
As the piezoelectric transformer 10, PT130A02 (product name) manufactured by Mitsui Petrochemical Industries, Ltd. was used. This piezoelectric transformer 10 can be driven at a resonance frequency of 120 kHz, and the impedance Z of the piezoelectric transformer 10 at that time is
Was Z = 323-j · 237 and | Z | = 423.
Then, as an AC power supply 40 (Vin), 5 V rms , 120 V
kHz. Capacitance element 50 (Cs
)), A ceramic capacitor of 14.1 nF is used, and 80 μH is used as the inductance element 60 (Lp).
Was used. 10 for load 45 (RL)
A 1 kΩ metal film resistor was used. At this time, the load 45
(RL) was supplied with 1.1 W and the power factor was 99.6%. A voltage of about 300 V was applied to the load 45 (RL), and the boost ratio was 60 times. Piezoelectric transformer 10
Since the boosting ratio of itself is about 15, it was boosted about four times by a circuit including the inductance element 60 (Lp) and the capacitance element 50 (Cs).

For comparison, as shown in FIG. 6, in the piezoelectric element drive circuit 124 in which an AC power supply 40 (Vin) is directly connected between the primary terminals 31 and 32 of the piezoelectric transformer 10, Element drive circuit 12 of the embodiment
2, a piezoelectric transformer 10 and an AC power supply 40 (Vin)
And a load of 45 (RL). At this time, the load 45
0.06 W was supplied to (RL), and the power factor was 72.7%. To supply 1 W to the load 45 (RL), the power supply voltage is 19.4 V as the AC power supply 40 (Vin).
Had to be used.

(Second Embodiment) FIG. 7 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to a second embodiment of the present invention.

In the present embodiment, a capacitance element 51 (Cp) is connected in parallel to the piezoelectric transformer 10 between the primary terminal 31 and the primary terminal 32 of the piezoelectric transformer 10, and the primary terminal 31 and the terminal The third embodiment is different from the first embodiment in that an inductance element 61 (Ls) is connected in series to the piezoelectric transformer 10 between the piezoelectric transformer 10 and the piezoelectric transformer 10. The operation principle is the same as in the first embodiment.

Now, referring again to FIG. 3, a reactance element 82 (jA) connected in parallel to the primary terminals 31 and 32 of the piezoelectric transformer 10 and a reactance element 81 (jB) connected in series. Find the applied voltage. The power supply voltage is set to V, and the reactance elements 81 (jB) and 82 (jA) from the AC power supply 40 (Vin), the piezoelectric transformer 10
And the imaginary component Im of the impedance Z looking at the load 45
If (Z) is zero and the real component Re (Z) is R,
The reactance element 82 (jA)

A voltage of VA = V · {1+ (B 2 / R 2 )} 1/2 (18) is applied to the reactance element 81 (jB).

VB = (BV) / R <| VA | (19) is applied.

Accordingly, it is required that the reactance element 82 (jA) connected in parallel has a higher withstand voltage than the reactance element 81 (jB) connected in series. Since the breakdown voltage is higher than that of the piezoelectric element drive circuit 122 of the first embodiment shown in FIG. 5, the piezoelectric element drive circuit 124 of the second embodiment shown in FIG. 7 has a higher breakdown voltage. Can be

(Third Embodiment) FIG. 8 is a circuit diagram for explaining a piezoelectric transformer driving circuit according to a third embodiment of the present invention. FIG. 9 is a circuit diagram showing a third embodiment of the present invention. FIG. 4 is a waveform chart for explaining an operation of the driving circuit of the piezoelectric transformer according to the embodiment.

In this embodiment, a DC power supply 41 and switches 71 and 7 are used instead of the AC power supply 40 of the first embodiment.
2 is different from the first embodiment in that an inductance element 62 is connected in parallel to the piezoelectric transformer 10 between the primary electrodes 11 and 12 of the piezoelectric transformer 10, and the capacitance element 52 is Since the piezoelectric transformer 10 is connected in series, the basic circuit operation is the same. Note that the switch 71 and the switch 72 are alternately turned on and off alternately, and a voltage as shown in FIG. 9A appears at both ends of the switch 72, and a current as shown in FIG. 9B is observed before the capacitance element 52.

(Fourth Embodiment) FIG. 10 is a circuit diagram for explaining a piezoelectric transformer driving circuit according to a fourth embodiment of the present invention.

In this embodiment, a capacitance element 53 is connected in parallel with the piezoelectric transformer 10 between the primary electrodes 11 and 12 of the piezoelectric transformer 10, and an inductance element 63 is connected in series with the piezoelectric transformer 10. This is different from the third embodiment. The operating principle is the same as in the third embodiment.

(Fifth Embodiment) FIG. 11 is a circuit diagram for explaining a piezoelectric transformer driving circuit according to a fifth embodiment of the present invention, and FIG. 12 is a circuit diagram showing a fifth embodiment of the present invention. FIG. 4 is a waveform chart for explaining an operation of the driving circuit of the piezoelectric transformer according to the embodiment.

In this embodiment, an inductance element 64 is connected in parallel with the piezoelectric transformer 10 between the primary electrodes 11 and 12 of the piezoelectric transformer 10, and a capacitance element 54 is connected in series with the piezoelectric transformer 10. Therefore, the basic circuit operation is the same as that of the third embodiment. The capacitance elements 55 and 56 are provided to divide the voltage of the DC power supply 41. Also,
A voltage as shown in FIG. 12A appears between the connection point of the capacitance elements 55 and 56 and the connection point of the switches 73 and 74, and the switch 73 and the switch 74 alternately turn on and off. A current as shown in FIG. 12B is observed.

(Sixth Embodiment) FIG. 13 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to a sixth embodiment of the present invention.

In this embodiment, a capacitance element 57 is connected in parallel with the piezoelectric transformer 10 between the primary electrodes 11 and 12 of the piezoelectric transformer 10, and an inductance element 65 is connected in series with the piezoelectric transformer 10. This is different from the fifth embodiment. The operation principle is the same as that of the fifth embodiment.

(Seventh Embodiment) FIG. 14 is a circuit diagram for explaining a piezoelectric transformer driving circuit according to a seventh embodiment of the present invention. FIG. 15 is a circuit diagram showing a seventh embodiment of the present invention. FIG. 4 is a waveform chart for explaining an operation of the driving circuit of the piezoelectric transformer according to the embodiment.

In this embodiment, the inductance element 66 is connected in parallel with the piezoelectric transformer 10 between the primary electrodes 11 and 12 of the piezoelectric transformer 10, and the capacitance element 58 is connected in series with the piezoelectric transformer 10. Therefore, the basic circuit operation is the same as that of the third embodiment. The switches 75 and 78 and the switches 76 and 77
Switches on and off alternately with switches 75 and 78
Are turned on and off at the same time, and switches 76 and 77 are turned on and off at the same time, so that a voltage as shown in FIG. 15A appears at both ends of the series connection of the inductance element 66 and the capacitance element 58, and before the capacitance element 58, A current as shown in FIG. 15B is observed.

(Eighth Embodiment) FIG. 16 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to an eighth embodiment of the present invention.

In this embodiment, a capacitance element 59 is connected in parallel with the piezoelectric transformer 10 between the primary electrodes 11 and 12 of the piezoelectric transformer 10, and an inductance element 67 is connected in series with the piezoelectric transformer 10. This is different from the seventh embodiment. The operation principle is the same as that of the seventh embodiment.

FIGS. 17A and 17B are views for explaining a piezoelectric transformer element suitably used in the piezoelectric transformer drive circuit of the present invention. FIG. 17A is a perspective view, and FIG. 17B is a sectional view. FIG. 17 (C) is a diagram showing a stress distribution, and FIG.
Is a diagram showing an amplitude distribution.

Upper surface 212 of piezoelectric ceramic substrate 210
A primary electrode 222 is provided on the left-hand side of the piezoelectric ceramic substrate 210, and a primary electrode 224 is provided on the lower surface 214 of the piezoelectric ceramic substrate 210 so as to face the primary electrode 222. On the upper surface 212 of the piezoelectric ceramic substrate 210, the primary end surface 21 is located at a distance from the primary end surface 216 by の of the length in the longitudinal direction L of the piezoelectric ceramic substrate 210.
The primary electrode 226 is provided from the position 6 to a position separated by a distance of 2/3 of the length in the longitudinal direction L of the piezoelectric ceramic substrate 210, and the primary electrode 226 is also provided on the lower surface 214 of the piezoelectric ceramic substrate 210 so as to face the primary electrode 226. A side electrode 228 is provided. The primary electrode 222 is provided apart from the primary electrode 226, and the primary electrode 224 is
And are provided separately.

The piezoelectric ceramic substrate 210 between the primary electrode 222 and the primary electrode 224 is polarized upward in the thickness direction T. The piezoelectric ceramic substrate 210 between the primary electrode 226 and the primary electrode 228 is polarized downward in the thickness direction T.

A secondary electrode 242 is provided on the upper surface 212 near the secondary end surface 217, and a secondary electrode 244 is provided on the lower surface 214 near the secondary end surface 217. The secondary region d of the piezoelectric ceramic substrate 210 is polarized leftward in the longitudinal direction L, which is the direction in which the upper surface 212 and the lower surface 214 extend.

The primary electrodes 222, 224, 22
6, 228 and the secondary electrodes 242, 244 extend from the longitudinal end face 218 to the longitudinal end face 219.
Extending over the entire width in the width direction W.

The primary electrodes 222 and 226 are connected to the terminal 31, the terminal 32 is connected to the primary electrodes 224 and 228 and one end of the load 45, and the other end of the load 45 is connected to the secondary electrode 242. .

In the piezoelectric transformer 10, the primary end face 21
Driving can be performed such that a vibration mode of, for example, 1.5 wavelength is set between the secondary end face 217 and the secondary side end face 217. In this case, the piezoelectric ceramic substrate 21
0, 1/6, and 5/6 of the length of the longitudinal direction L are nodes of the longitudinal vibration, 201, 202,
203. In the piezoelectric transformer 10, the left-hand side 2/3 is the primary side area c, and the right-hand side 1/3.
Is the secondary region d.

In this piezoelectric transformer 10, between the primary electrodes 222 and 224 and the primary electrodes 226 and 228
When a voltage is applied therebetween, in the primary side region c, an electric field is applied in the thickness direction T, and longitudinal vibration in the longitudinal direction L is excited by a piezoelectric transverse effect displaced in a direction perpendicular to the polarization direction, and the piezoelectric transformer element The whole 200 vibrates. Further, on the secondary side, a mechanical strain occurs in the longitudinal direction L, and a potential difference occurs in the polarization direction, so that the secondary electrode 242, 244 to the primary electrode 222, 224 and the primary electrode 226,
A voltage having the same frequency as the primary voltage applied between 228 is extracted. When a drive voltage having a frequency equal to the resonance frequency of the piezoelectric transformer 10 is applied between the primary electrodes 222 and 224 and between the primary electrodes 226 and 228, a very high step-up ratio can be obtained.

In the piezoelectric transformer 10,
Since the primary-side electrode 226 and the primary-side electrode 228 are provided in addition to the primary-side electrode 222 and the primary-side electrode 224, the primary-side electrode area becomes larger, and the piezoelectric transformer 10
Input impedance becomes small. As a result, electric energy is easily supplied to the piezoelectric transformer 10 from a power supply (not shown).

Further, the primary electrode 222 and the primary electrode 2
24, the piezoelectric ceramic substrate 210 has a thickness direction T
, The piezoelectric ceramic substrate 210 between the primary electrode 226 and the primary electrode 228 is polarized downward in the thickness direction T, and the primary electrodes 222 and 226 are connected in common, and the primary electrode 224 and Since the 228 is connected in common, the resonance of the entire piezoelectric ceramics substrate 210 excited by the piezoelectric ceramics substrate 210 between the primary side electrode 222 and the primary side electrode 224 and the primary side electrode 226 and the primary side electrode 228 The resonance of the entire piezoelectric ceramic substrate 210 which is excited by the piezoelectric ceramic substrate 210 during the period increases the other resonance with each other. Therefore, the input electric energy can be more efficiently converted into mechanical elastic energy on the primary side.

The primary electrodes 226 and 228 are provided between the primary electrodes 222 and 224 and the secondary electrodes 242 and 244. By providing the primary electrodes 226 and 228 in this manner, the secondary region d can be shortened in the longitudinal direction L, and as a result, the output impedance of the piezoelectric transformer 10 can be reduced, and the output impedance of the piezoelectric transformer 10 can be reduced. it can. When the output impedance of the piezoelectric transformer 10 decreases, the voltage that can be applied to the load 45 connected to the secondary side of the piezoelectric transformer 10 increases.

The driving circuit of the piezoelectric transformer of the present invention is as follows.
It is suitably applied to the piezoelectric transformer described with reference to FIG. When the piezoelectric transformer having this structure is used, as described above, the input impedance and the output impedance of the piezoelectric transformer are small, and the input electric energy can be more efficiently converted into mechanical elastic energy on the primary side. Therefore, the inductance used in the drive circuit of the present invention can be reduced,
For example, the size can be reduced to about 1/2, and the size of the inductance element can be reduced, for example, to about 1/2.

In the piezoelectric transformer driving circuits shown in FIGS. 1 to 16, the primary electrodes 222 and 226 are collectively represented by the primary electrode 11, and the primary electrodes 224 and 228 are represented by the primary electrode 12 together. The secondary electrode 242 is represented by the secondary electrode 13.

[0093]

According to the present invention, it is possible to provide a piezoelectric element drive circuit capable of supplying a large amount of electric power at a low voltage at a low cost.

Further, there is provided a piezoelectric element driving circuit capable of improving a power factor and reducing a load on an active element such as a driving transistor.

Further, it is possible to provide an inexpensive piezoelectric element drive circuit having a variable boost ratio.

Therefore, irrespective of the structure of the piezoelectric element, any combination of external reactance elements can supply any electric power at an arbitrary voltage. The application range of the device will be dramatically expanded.

[Brief description of the drawings]

FIG. 1 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to the present invention.

FIG. 2 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to the present invention.

FIG. 3 is a circuit diagram for explaining a driving circuit of the piezoelectric transformer of the present invention.

FIG. 4 is a circuit diagram for explaining a driving circuit of the piezoelectric transformer of the present invention.

FIG. 5 is a circuit diagram for explaining a driving circuit of the piezoelectric transformer according to the first embodiment of the present invention.

FIG. 6 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer for comparison.

FIG. 7 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to a second embodiment of the present invention.

FIG. 8 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to a third embodiment of the present invention.

FIG. 9 is a waveform chart for explaining the operation of the driving circuit for the piezoelectric transformer according to the third embodiment of the present invention.

FIG. 10 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to a fourth embodiment of the present invention.

FIG. 11 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to a fifth embodiment of the present invention.

FIG. 12 is a waveform chart for explaining an operation of a driving circuit of a piezoelectric transformer according to a fifth embodiment of the present invention.

FIG. 13 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to a sixth embodiment of the present invention.

FIG. 14 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to a seventh embodiment of the present invention.

FIG. 15 is a waveform chart for explaining an operation of a drive circuit for a piezoelectric transformer according to a seventh embodiment of the present invention.

FIG. 16 is a circuit diagram for explaining a driving circuit of a piezoelectric transformer according to an eighth embodiment of the present invention.

FIG. 17 is a diagram for explaining a piezoelectric transformer suitably used in the piezoelectric transformer drive circuit of the present invention.
7A is a perspective view, FIG. 17B is a cross-sectional view, and FIG.
17C is a diagram illustrating a stress distribution, and FIG. 17D is a diagram illustrating an amplitude distribution.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Piezoelectric transformer 11, 12 ... Primary electrode 13 ... Secondary electrode 20 ... Driving circuit 31, 32, 33, 34 ... Terminal 40 ... AC power supply 41 ... DC power supply 45 ... Load 50-59 ... Capacitance element 60-67 ... Inductance elements 71-78 ... Switches 81, 81 ', 82 ... Reactance elements 100, 112, 114, 122, 124, 126, 1
32, 134, 142, 144, 152, 154: piezoelectric transformer drive circuits 201, 202, 203: nodes of vibration 210: piezoelectric ceramic substrate 212: upper surface 214: lower surface 216: primary side end surface 217: secondary side end surface 218, 219 ... Longitudinal end faces 222,224,226,228 ... Primary electrodes 242,244 ... Secondary electrodes W ... Width direction T ... Thickness direction L ... Longitudinal direction

Claims (18)

[Claims]
1. A piezoelectric element driving circuit comprising: a piezoelectric element; a load connected to the piezoelectric element; and a power supply for driving the piezoelectric element and the load. In series and /
Or, by connecting one or more reactance elements in parallel, the driving frequency of the piezoelectric element is higher than the real component of the first impedance when the load is viewed from the electric input terminal of the piezoelectric element. A real component of the second impedance when a circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed, is reduced.
2. A piezoelectric element driving circuit comprising: a piezoelectric element; and a power supply for driving the piezoelectric element and a load to be connected to the piezoelectric element. /
Or, by connecting one or more reactance elements in parallel, the driving frequency of the piezoelectric element is higher than the real component of the first impedance when the load is viewed from the electric input terminal of the piezoelectric element. A real component of the second impedance when a circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed, is reduced.
3. The driving frequency of the piezoelectric element by connecting the one or more reactance elements,
The imaginary component of the first impedance when the load was viewed from the electric input terminal of the piezoelectric element was substantially canceled, and the one or more reactance elements, the piezoelectric element, and the load were provided from the power supply. The second when we look at the circuit
3. The piezoelectric element drive circuit according to claim 1, wherein the imaginary component of the impedance of the piezoelectric element is substantially zero.
4. The piezoelectric element driving circuit according to claim 3, wherein the absolute value of the imaginary part of the second impedance is set to 0.2 or less of the absolute value of the second impedance.
5. The one or more reactance elements electrically connected in series and / or parallel to the electric input terminal of the piezoelectric element, the one or more reactance elements being electrically connected in parallel to the electric input terminal of the piezoelectric element. 5. The apparatus according to claim 1, further comprising a first reactance element connected to the piezoelectric element, and a second reactance element electrically connected in series to the electric input terminal of the piezoelectric element.
The piezoelectric element drive circuit according to any one of the above.
6. The piezoelectric element drive circuit according to claim 5, wherein said first reactance element is an inductance element, and said second reactance element is a capacitance element.
7. The piezoelectric element drive circuit according to claim 5, wherein said first reactance element is a capacitance element, and said second reactance element is an inductance element.
8. The piezoelectric element driving circuit according to claim 1, wherein the piezoelectric element is a piezoelectric transformer.
9. The piezoelectric element drive circuit according to claim 1, wherein the load is a cold cathode tube.
10. A liquid crystal display device incorporating the piezoelectric element drive circuit according to claim 1.
11. An electronic device comprising the piezoelectric element drive circuit according to claim 1.
12. The piezoelectric element drive circuit according to claim 1, wherein said piezoelectric element is an ultrasonic transducer.
13. A piezoelectric element driving circuit comprising: a piezoelectric element; a load connected to the piezoelectric element; and a power supply for driving the piezoelectric element and the load. In series and /
Or by connecting one or more reactance elements in parallel, at the driving frequency of the piezoelectric element, the real component of the first impedance when the load is viewed from the electric input terminal of the piezoelectric element, A piezoelectric element driving circuit, wherein a real component of a second impedance is different when a circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from a power supply.
14. A piezoelectric element drive circuit comprising: a piezoelectric element; and a power supply for driving the piezoelectric element and a load to be connected to the piezoelectric element. /
Or by connecting one or more reactance elements in parallel, at the driving frequency of the piezoelectric element, the real component of the first impedance when the load is viewed from the electric input terminal of the piezoelectric element, A piezoelectric element driving circuit, wherein a real component of a second impedance is different when a circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from a power supply.
15. An imaginary component of the first impedance when the load is viewed from the electric input terminal of the piezoelectric element at a driving frequency of the piezoelectric element by connecting the one or more reactance elements. The imaginary component of the second impedance when the circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from the power supply is substantially zero. 3. The piezoelectric element drive circuit according to 1 or 2.
16. A piezoelectric element drive circuit comprising: a piezoelectric element; a load connected to the piezoelectric element; and a power supply for driving the piezoelectric element and the load. In series and /
Or by connecting one or more reactance elements in parallel, at the drive frequency of the piezoelectric element, removing the reactance component of the first impedance when the load is viewed from the electric input terminal of the piezoelectric element, A piezoelectric element drive circuit, wherein a reactance component of a second impedance when the circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from the power source is substantially zero.
17. A piezoelectric element drive circuit comprising: a piezoelectric element; and a power supply for driving the piezoelectric element and a load to be connected to the piezoelectric element, wherein the piezoelectric element is electrically connected in series with an electric input terminal of the piezoelectric element. /
Or by connecting one or more reactance elements in parallel, at the drive frequency of the piezoelectric element, removing the reactance component of the first impedance when the load is viewed from the electric input terminal of the piezoelectric element, A piezoelectric element drive circuit, wherein a reactance component of a second impedance when the circuit including the one or more reactance elements, the piezoelectric element, and the load is viewed from the power source is substantially zero.
18. The piezoelectric element drive circuit according to claim 13, wherein said piezoelectric element is a piezoelectric transformer.
JP34659196A 1996-12-09 1996-12-09 Piezoelectric element drive circuit Withdrawn JPH10174436A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP34659196A JPH10174436A (en) 1996-12-09 1996-12-09 Piezoelectric element drive circuit

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP34659196A JPH10174436A (en) 1996-12-09 1996-12-09 Piezoelectric element drive circuit

Publications (1)

Publication Number Publication Date
JPH10174436A true JPH10174436A (en) 1998-06-26

Family

ID=18384470

Family Applications (1)

Application Number Title Priority Date Filing Date
JP34659196A Withdrawn JPH10174436A (en) 1996-12-09 1996-12-09 Piezoelectric element drive circuit

Country Status (1)

Country Link
JP (1) JPH10174436A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6181031B1 (en) 1997-11-28 2001-01-30 Stmicroelectronics S.R.L. System for driving a reactive load
US6538346B2 (en) 1998-11-25 2003-03-25 Stmicroelectronics S.R.L. System for driving a reactive load
WO2007145127A1 (en) 2006-06-15 2007-12-21 Koichi Hirama Composite resonator
EP3041123A1 (en) * 2013-08-29 2016-07-06 Sumitomo Electric Industries, Ltd. Transformer

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6181031B1 (en) 1997-11-28 2001-01-30 Stmicroelectronics S.R.L. System for driving a reactive load
US6538346B2 (en) 1998-11-25 2003-03-25 Stmicroelectronics S.R.L. System for driving a reactive load
WO2007145127A1 (en) 2006-06-15 2007-12-21 Koichi Hirama Composite resonator
US8179209B2 (en) 2006-06-15 2012-05-15 Koichi Hirama Complex resonance circuit
EP3041123A1 (en) * 2013-08-29 2016-07-06 Sumitomo Electric Industries, Ltd. Transformer
EP3041123A4 (en) * 2013-08-29 2017-05-10 Sumitomo Electric Industries, Ltd. Transformer
US10320305B2 (en) 2013-08-29 2019-06-11 Sumitomo Electric Industries, Ltd. Transformer

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