JPH10256881A - Pulse generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pulse generator that drives suitably an electromechanical conversion element which is made small in size, has a small number of components and less power consumption. SOLUTION: When an intermittent current is supplied from a low voltage power supply 11 to a primary side of a transformer 12 with an inductance L through a chopping operation of a switching circuit 14, an induced voltage ΔV based on a counter electromotive force generated in the inductance L is charged accumulatingly in a piezoelectric element 18 and an inter-electrode voltage of the piezoelectric element 18 is increased. When the voltage reaches a prescribed peak level Vp, a switching circuit 17 is closed to cause short-circuit and discharge, then a nearly trapezoidal pulse is generated. A control section 16 controls the chopping operation of the switching circuit 14 and monitors the inter-electrode voltage of the piezoelectric element 18 and controls the switching circuit 17 to be closed when the voltage reaches the peak level Vp.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pulse generator,
In particular, the present invention relates to a pulse generator suitable for driving a driving device using an electromechanical transducer.

[0002]

2. Description of the Related Art For driving a camera or other components constituting a precision instrument, a piezoelectric element is caused to undergo expansion and contraction displacement, the expansion and contraction displacement is transmitted to a driving member, and driven by a moving member frictionally coupled to the driving member. A linear actuator and a rotary actuator configured to move a member are known (JP-A-4-69070, JP-A-63-1107).
No. 4).

FIG. 10 shows an example of a driving apparatus applied to driving a zoom lens mounted on a camera, in which a supporting member 72 for supporting a lens barrel 71 of a lens as a driven member is slidably fitted. The portions 72a and 72b are slidably and frictionally fitted to the drive shaft 73 and fitted. The drive shaft 73 is supported by the support portions 75 and 76 of the frame 77 so as to be displaceable in the axial direction. One end of the piezoelectric element 78 displaced in the thickness direction is fixed to an axial end of the drive shaft 73.
The other end of the piezoelectric element 78 is fixed to the frame 77,
The drive shaft 73 is displaced in the axial direction by the displacement in the thickness direction.

[0004] Reference numeral 74 denotes a leaf spring, which is attached to the sliding fitting portions 72a and 72b of the support 72 by small screws (not shown) as shown in FIG.
0 is fixed from below. A bent portion 74a that is bent upward is formed at the center of the leaf spring 74,
This is because the bent portion 74a is pressed against the drive shaft 73 to generate an appropriate frictional force at the contact portion.

In the driving mechanism shown in FIG. 10, a driving pulse having a waveform (trapezoidal waveform) composed of a gentle rising portion and a rapid falling portion following this is applied to the piezoelectric element 78 as shown in FIG. Then, at the rising portion of the drive pulse, the piezoelectric element 78 gently expands in the thickness direction and generates displacement, and the drive shaft 73 moves gently in the direction of arrow a in the axial direction.

At this time, the frictional force between the drive shaft 73 and the sliding fitting portions 72a and 72b of the support 72 and the frictional force between the drive shaft 73 and the bent portion 74a of the leaf spring 74 are driven by the piezoelectric element 78. If the force is not more than the force applied to the shaft 73, the support 7
2 moves in the direction of arrow a together with the drive shaft 73 while being frictionally coupled to the drive shaft 73, and the lens barrel 71 moves in the direction indicated by arrow a.

On the other hand, at the rapid falling portion of the drive pulse, the piezoelectric element 78 rapidly contracts in the thickness direction, so that the drive shaft 73 moves rapidly in the axial direction in the direction opposite to the arrow a. At this time, the sliding fitting portions 72a, 7
The support 72 supported by the support 2b has a frictional force between the drive shaft 73 and the sliding fitting portions 72a and 72b of the support 72 due to its inertia, and a bending portion 74a of the drive shaft 73 and the leaf spring 74.
The lens barrel 71 does not move because the lens barrel 71 stays at that position by overcoming the frictional force of the lens barrel 71.

The drive pulse having the above-mentioned waveform (trapezoidal waveform) is continuously applied to the piezoelectric element 78, so that the lens barrel 7
1 can be continuously moved in the direction indicated by arrow a. In order to move the lens barrel 71 in the direction opposite to the arrow a, a drive pulse having a waveform (trapezoidal waveform) composed of a rapid rising portion and a gentle falling portion as shown in FIG. This can be achieved by applying a voltage to the piezoelectric element 78.

[0009]

However, since a complicated circuit is used in the pulse generator for generating the driving pulse, the following problems have been pointed out.

First, since a relatively high voltage (several tens of volts) is required as a peak voltage of a drive pulse applied to the piezoelectric element, a low voltage power supply (several volts) such as a battery is used as a power supply.
In the case of using, a booster circuit having a complicated configuration for generating a high voltage is required.

Second, when a constant current circuit, a switching circuit, and a timing circuit for controlling the control timing are combined as a circuit for generating a drive pulse having a trapezoidal waveform, the entire device becomes large and the power consumption becomes large. thing.

An object of the present invention is to provide a new drive pulse generator which solves the above-mentioned problems of the conventional pulse generator.

[0013]

According to the present invention, an inductance element and a first switching means are connected in series to a power supply, and the inductance element and the first switching means are connected to each other. A pulse generating circuit that connects a capacitance element between a connection point with the means and a connection point between the first switching means and the power supply, and connects the second switching means in parallel with the capacitance element; and a control means. The control means performs a chopping operation of intermittently turning on / off the first switching means to accumulate and accumulate the back electromotive force generated in the inductance element in the capacitance element, and the accumulated electric charge becomes a predetermined value. It is characterized in that the control is performed such that the second switching means is turned on when it reaches the voltage to discharge.

[0014] The inductance element may be a primary winding of a coil or a transformer, and the capacitance element may be an electromechanical conversion element, specifically, a piezoelectric element.

Further, the first switching means and the second switching means may be switching means composed of semiconductor elements.

Further, the control means is a micro computer.
And performs a chopping operation for intermittently turning on / off the first switching means at predetermined time intervals, and monitors whether the charge accumulated in the capacitance element reaches a predetermined value. Then, control is performed so that the second switching means is turned on when the predetermined value is reached.

According to an eighth aspect of the present invention, there is provided a pulse generator suitable for a driving mechanism which generates a telescopic displacement by applying a pulse voltage to an electromechanical transducer and drives a mechanism member by the generated displacement. And the first switching means are connected in series to the power supply, and the inductive circuit element and the first switching means are connected in series.
A capacitive electromechanical transducer is connected between a connection point with the switching circuit element and a connection point between the first switching means and the power supply, and a second switching element is connected in parallel with the capacitive electromechanical transducer. A pulse generating circuit connected to the first switching means; and a control means, wherein the control means performs a chopping operation for intermittently turning on / off the first switching means and generates a back electromotive force generated in the inductive circuit element. Is accumulated in the capacitive electromechanical transducer, and when the accumulated electric charge reaches a predetermined value, the second switching means is turned on to perform control.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a pulse generating circuit which is the basis of the present invention will be described with reference to FIG. As shown in FIG. 1, a coil 2 having an inductance L and a switch 3 are connected in series to a low-voltage power supply 1, and when the switch 3 is turned on / off, the coil L is turned on and off by the coil L when the switch 3 is turned off. 2 is applied to the piezoelectric element 4 and a small voltage Δ is applied between the electrodes of the piezoelectric element 4.
V charge is accumulated. This is because the piezoelectric element 4 functions as a capacitor.

When the chopping operation of turning on / off the switch 3 at a predetermined cycle T is continuously repeated, the piezoelectric element 4
Is charged accumulatively with the minute voltage ΔV due to the back electromotive force generated at both ends of the coil 2, and the voltage V between the electrodes of the piezoelectric element 4 is charged.
Rises. When the voltage V between the electrodes of the piezoelectric element 4 reaches a predetermined peak voltage Vp, the on / off operation of the switch 3 is stopped, and after a lapse of a predetermined time, the switch 5 is turned on to short-circuit the electrodes of the piezoelectric element 4. Then, the voltage V applied to the piezoelectric element 4 rapidly drops from the peak voltage Vp to zero.
By repeating the charge / discharge operation every time a predetermined time elapses, a substantially trapezoidal pulse can be generated.

According to this method, a high voltage can be generated using the back electromotive force generated at both ends of the coil by the inductance L of the coil and the piezoelectric element functioning as a capacitor, and a constant current circuit or the like is used. Without this, a substantially trapezoidal pulse can be generated only by the switching circuit and its control circuit.

A first embodiment of the present invention will be described with reference to FIGS. 2 shows a configuration of a pulse generating circuit for generating a trapezoidal waveform pulse. FIG. 3 (a) shows an output pulse waveform, and FIGS. 3 (b) and 3 (c) show operation timings of the switching circuit. FIG.

As shown in FIG. 2, in the pulse generating circuit, a primary winding 12p of a transformer 12 and a switching circuit 14 are connected in series to a low voltage power supply 11. A piezoelectric element 18 is connected in series to the secondary winding 12s of the transformer 12, and a switching circuit 17 is connected in parallel to both electrode ends of the piezoelectric element 18. Switching circuits 14, 17
Is constituted by a semiconductor switching element, and is turned on / off at the operation timings shown in FIGS. 3B and 3C by a control unit 16 constituted by a microcomputer.

When the switching circuit 14 is turned on, a current flows through the primary winding 12p of the transformer 12, and the primary winding 1
Energy is stored in 2p. At this time, the transformer 12
The induced voltage induced in the secondary winding 12s is the diode 15
Occurs in the direction of applying a reverse bias to the secondary winding 1
The induced voltage induced in 2s is cut off by the diode 15,
It is not applied to the piezoelectric element 18.

When the switching circuit 14 is turned off, the back electromotive force generated by the inductance of the primary winding 12p of the transformer 12 generates an induced voltage in the secondary winding 12s. The voltage generated in the secondary winding 12s is applied to the piezoelectric element 18 via the diode 15, and the electric charge of the minute voltage ΔV1 is accumulated between the electrodes of the piezoelectric element 18. At this time, the switching circuit 17 is off. Since the electric charge stored in the piezoelectric element 18 applies a reverse bias to the diode 15, the electric charge is stored without discharging. By increasing the winding ratio between the primary winding 12p and the secondary winding 12s of the transformer 12,
The voltage induced in the next winding 12s can be increased.

When the on / off operation (chopping operation) of the switching circuit 14 described above is repeated for a period t0, the voltages .DELTA.V1, .DELTA.V2... Are sequentially applied to the piezoelectric element 18 as shown in FIG. Then, the charges are accumulated, and the applied voltage V to the piezoelectric element 18 gradually increases.
The voltage V applied to the piezoelectric element 18 is monitored by the control unit 16, and when a predetermined peak voltage Vp is reached, the control unit 16
Stops the on / off operation (chopping operation) of the switching circuit 14. The electric charge stored in the piezoelectric element 18 is stored without discharging.

After the predetermined time t1 has elapsed, the control section 16 turns on the switching circuit 17 to short-circuit the electrodes of the piezoelectric element 18, and the voltage V applied to the piezoelectric element 18 rapidly decreases from the peak voltage Vp. To zero.

Immediately before the lapse of the predetermined time t2, the control unit 16 starts the on / off operation (chopping operation) of the switching circuit 14 again. By repeating the charge / discharge operation described above, a substantially trapezoidal drive pulse as shown in FIG. 3A can be generated. Predetermined times t1 and t2
Is caused to generate a substantially trapezoidal pulse.

The rate at which the voltage V applied to the piezoelectric element 18 increases depends on the on / off duty of the switching circuit 14.
It can be adjusted by changing the tee ratio. The longer the ON period, the larger the rate of increase of the voltage V. In order to smooth the rate of change of the voltage V, it is necessary to turn on / off the switching circuit 14.
By shortening the OFF cycle, the rate of change can be reduced, and the rate of change can be smoothed.

In the above-described pulse generating circuit, as shown in FIG. 3A, a substantially trapezoidal pulse composed of a gentle rising portion and a rapid falling portion is generated. In order to achieve the change of the driving direction by changing the pulse waveform, it is necessary to generate a pulse having a substantially trapezoidal waveform including a rapid rising portion and a gentle falling portion. For this purpose, the ON / OFF duty ratio of the switching circuit 14 is adjusted to extend the ON period so as to have a rapid rising portion, and at the time of discharging by the switching circuit 17 gently through a resistor. By giving a good discharge characteristic, it is possible to generate a pulse having a substantially trapezoidal waveform including a rapid rising portion and a gentle falling portion.

The diode 15 shown in FIG. 2 can be replaced by a switching element having the same function.

In the pulse generation circuit shown in FIG. 2, when the switching circuit 14 is turned off,
The induced voltage induced in the secondary winding 12s by the back electromotive force due to the inductance of the primary winding 12p is used. However, when the switching circuit 14 is on, the primary winding 12p of the transformer 12 is turned on. An induced voltage induced in the secondary winding 12s by the flowing current may be used. In this case, the polarity of the induced voltage induced in the secondary winding 12s is reversed.

Next, a second embodiment of the present invention will be described. In the second embodiment, a coil is used instead of the transformer 12 of the pulse generating circuit of the first embodiment shown in FIG. 2, and a switching circuit is used instead of the diode 15.

FIG. 4 shows the configuration of a pulse generating circuit according to the second embodiment. FIG. 5 (a) shows an output pulse waveform, and FIGS. 5 (b), (c) and (d) show switching. FIG. 3 is a diagram illustrating operation timing of a circuit.

In this pulse generation circuit, a coil 13 and a switching circuit 14 are connected in series to a low-voltage power supply 11,
A switching circuit 19 and a piezoelectric element 18 are connected in series between a connection point P between the coil 13 and the switching circuit 14 and a connection point Q between the switching circuit 14 and the negative side of the low-voltage power supply 11. A switching circuit 17 is connected in parallel to both electrode ends of the piezoelectric element 18.

The switching circuits 14, 17, and 19 are composed of semiconductor switching elements, and are controlled by a control unit 16 composed of a micro computer as shown in FIGS. 5B and 5C.
On / off control is performed at the timing shown in FIG.

Switching circuit 14 for ON / OFF operation
Changes from on to off, the current flowing through the coil 13 is cut off, and a back electromotive force is generated at the terminal P of the coil 13 due to its inductance. At this time, the switching off / off operation is synchronized with the on / off operation of the switching circuit 14.
Since the switching circuit 19 that operates on changes from off to on, the generated back electromotive force is applied to the switching circuit 19.
Is applied to the piezoelectric element 18, and the electric charge of the minute voltage ΔV 1 is accumulated between the electrodes of the piezoelectric element 18. At this time, since the switching circuit 17 is turned off, the charge is stored without being discharged.

When the on / off operation (chopping operation) of the switching circuit 14 is repeated for a period t0, FIG.
As shown in (a) of FIG.
.. Are sequentially applied to accumulate charges, and the applied voltage V to the piezoelectric element 18 gradually increases. Piezoelectric element 18
The applied voltage V is monitored by the control unit 16 and when it reaches a predetermined peak voltage Vp, the control unit 16 turns on / off the switching circuit 14 (chopping operation) and turns off / on the switching circuit 19. Stop the operation. The electric charge stored in the piezoelectric element 18 is stored without discharging.

After a lapse of a predetermined time t1, the control section 16 turns on the switching circuit 17 to short-circuit the electrodes of the piezoelectric element 28, and the voltage V applied to the piezoelectric element 18 rapidly decreases from the peak voltage Vp. It becomes zero.

Immediately before the lapse of the predetermined time t2, the control section 16 starts the on / off operation of the switching circuit 14 and the off / on operation of the switching circuit 19 again. By repeating the charge / discharge operation, a substantially trapezoidal drive pulse as shown in FIG. 5A can be generated.

FIG. 6 specifically shows the switching circuits 14 and 17 in the pulse generating circuit shown in FIG. The switching circuit 14 includes a transistor T
The switching circuit 17 comprises a transistor TR2 and resistors R3 and R4. The resistor R5 is for setting a discharge characteristic when discharging the electric charge accumulated in the piezoelectric element 18. The diode 15 receives the induced voltage generated on the secondary side of the transformer 12 while the transistor TR1 is on.
2 acts as a reverse voltage on the emitter of
Since the performance degradation and destruction of 2 occur, it also serves as a protection diode to protect it.

The switching circuit 14 turns on when the signal Va output from the control unit 16 to the base of the transistor TR1 is "H", and turns off when the signal Va is "L". The switching circuit 17 controls the transistor TR2 from the control unit 16.
Is turned on when the signal Vb output to the
It turns off when b is "L". The pulse waveform and operation timing output from this pulse generation circuit are the same as the pulse waveform and operation timing described above with reference to FIGS. 3A and 3B and 3C, and therefore description thereof is omitted.

FIG. 7 shows the pulse generation circuit shown in FIG. 6 in which the polarity of the voltage applied to the electrodes of the piezoelectric element 18 is reversed to invert the expansion and contraction characteristics with respect to the applied voltage, and the direction of movement of the driving device can be switched. FIG.

Normally, since the piezoelectric element 18 has been subjected to a polarization process, the applied voltage versus displacement characteristic follows a well-known butterfly curve. Therefore, by using the reverse polarity voltage applied to the piezoelectric element 18 as a voltage in a range in which the contraction displacement characteristics can be obtained, the expansion / contraction characteristics can also be reversed by reversing the polarity of the applied voltage.

FIG. 8A shows the pulse waveform output from the pulse generation circuit shown in FIG. 7, and FIG. 8B and FIG.
FIG. 4D is a diagram showing the operation timing of the switching circuit. In this pulse generation circuit, the switching circuit 14 is composed of a transistor TR1, resistors R1 and R2,
The point that the signal Va output to the source turns on when the signal Va is “H” and turns off when the signal Va is “L” is the same as the pulse generating circuit shown in FIG.

The electrode a of the piezoelectric element 18 is a diode 15,
The transistor TR4 is connected to the secondary side of the transformer 12 via a transistor TR4, and a switching circuit 17a composed of a transistor TR2 and resistors R3 and R4 is connected. The electrode b of the piezoelectric element 18 is connected to the secondary side of the transformer 12 via a diode 15 and a transistor TR5, and a switching circuit 17b composed of a transistor TR3 and resistors R6 and R7 is connected. The electrodes a and b of the piezoelectric element 18 are connected to diodes 11, 1 and 1, respectively.
2 are connected in the opposite direction. The resistors R5 and R8 are resistors for setting the discharge characteristics of the electric charge of the piezoelectric element 18, and may be omitted in some cases.

In the above configuration, as shown in FIG. 8D, in the period T1, "H" of the signal Vb 'is initially supplied from the control unit 16 to the base of the transistor TR3.
The transistors TR3 and TR4 are turned on, the switching circuit 17b is turned on, and a voltage is applied to the electrode a of the piezoelectric element 18 via the diode 15 and the transistor TR4.
The electrode b of the piezoelectric element 18 is grounded via the resistor R8 and the diode 11.

A signal Va is supplied from the control unit 16 to the base of the transistor TR1 of the switching circuit 14 during the period t0, and the signal Va is supplied to the primary side of the transformer 12 by the on / off operation (chopping operation) of the switching circuit 14. An electromotive force is generated, and an induced voltage is generated on the secondary side.

In the periods t0 and t1, the "L" level of the signal Vb is supplied from the control unit 16 to the base of the transistor TR2 of the switching circuit 17a.
Since R5 is turned off, an induced voltage is applied to the electrode a of the piezoelectric element 18 via the transistor TR4, and electric charges are accumulated.

After the lapse of the periods t0 and t1, the signal Vb becomes "H" and the transistors TR2 and TR5 are turned on. Therefore, the electrode a of the piezoelectric element 18 is grounded via the resistor R5 and the diode 12, and the electric charge is rapidly increased. Is discharged.

Thus, the positive electrode (+) of FIG. 8A is applied to the electrode a of the piezoelectric element 18 from the secondary side of the transformer 12.
Since a substantially trapezoidal pulse on the side is supplied, driving in a predetermined first direction can be performed.

Next, as shown in FIG.
In step 2, "H" of the signal Vb is supplied from the control unit 16 to the base of the transistor TR2, and the transistors TR2, T2
R5 is on. In the period t3, the control unit 1
From 6, a signal Va is applied to the base of the transistor TR 1 of the switching circuit 14 during the period t 3, and a back electromotive force is generated on the primary side of the transformer 12 by the on / off operation (chopping operation) of the switching circuit 14. , An induced voltage is generated on the secondary side.

"L" of the signal Vb 'is supplied from the control unit 16 to the base of the transistor TR3, and the transistor TR3 is turned on.
3. Since TR4 is turned off, a voltage is applied to the electrode b of the piezoelectric element 18 via the transistor TR5 to accumulate electric charges.

After the elapse of the period t4, the signal Vb 'becomes "H", the transistors TR3 and TR4 are turned on, and the electric charge of the electrode b of the piezoelectric element 18 is discharged through the resistor R8 and the diode 11.

As a result, a substantially trapezoidal pulse on the minus (-) side in FIG. 8A is supplied to the electrode b of the piezoelectric element 18 from the secondary side of the transformer 12, so that the direction opposite to the above direction is supplied. (The second direction).

In the above circuit, the transistor TR4
, TR5 are controlled on / off by transistors TR3 and TR2, respectively, but may be configured to be controlled by the control unit 16.

FIG. 9 shows the pulse generation circuit shown in FIG. 6 in which the transformer 12 is replaced by a coil 13 and the polarity of the voltage applied to the electrodes of the piezoelectric element 18 is reversed to invert the expansion and contraction characteristics with respect to the applied voltage. This is a pulse generation circuit that can reversely switch the moving direction of the device. The pulse waveform output from this pulse generation circuit is the same as the waveform shown in FIG. 8A, and the operation timing of the switching circuit is shown in FIGS. 8B, 8C and 8D. Since the operation timing is the same, the following description will be made with reference to FIGS. 8A and 8B, 8C, and 8D.

In this pulse generation circuit, the switching circuit 14 comprises a transistor TR1 and resistors R1 and R2, and the control unit 16 determines that the transistor TR1
Is turned on when the signal Va output to the
The point that a is turned off when “a” is “L” is the same as the pulse generation circuit shown in FIG.

The electrode a of the piezoelectric element 18 is a transistor TR
6. A switching circuit 17a comprising a transistor TR2 and resistors R3 and R4 is connected to the coil 13 via a diode 15. The electrode b of the piezoelectric element 18 is connected to the transistor TR7 and the diode 15
To the coil 13 and the transistor T
A switching circuit 17b composed of R3 and resistors R6 and R7 is connected. The transistors TR2 and TR6 and the transistors TR3 and TR7 are turned off when one is on, and turned on when one is off.

Diodes 12 and 11 are connected to the electrodes a and b of the piezoelectric element 18 in opposite directions.
The resistors R5 and R8 are resistors for setting the discharge characteristics of the electric charge of the piezoelectric element 18, and may be omitted in some cases. Diode 13
The diode 14 prevents the resistance R8 from affecting the ON operation of TR7, and the diode 14 prevents the resistance R5 from affecting the ON operation of TR6.

In the above configuration, as shown in FIG. 8D, in the period T1, the control unit 16 initially outputs the signal V
The "H" of b 'is applied to the base of the transistor TR3, the transistor TR3 is turned on and TR7 is turned off, the switching circuit 17b is turned on, and the electrode b of the piezoelectric element 18 is connected to the resistor R8 and the diode 13, And ground through a diode 11.

A signal Va is supplied from the control unit 16 to the base of the transistor TR1 of the switching circuit 14 during the period t0, and a back electromotive force is generated in the coil 13 by the on / off operation (chopping operation) of the switching circuit 14. I do.

In the periods t0 and t1, the "L" level of the signal Vb is supplied from the control unit 16 to the base of the transistor TR2 of the switching circuit 17a, and the transistor TR2 is turned off and the transistor TR6 is turned on. The back electromotive force is applied to the electrode a and stored.

After the lapse of the periods t0 and t1, the signal Vb becomes "H" and the transistor TR2 is turned on and the transistor TR6 is turned off, so that the electrode a of the piezoelectric element 18 is connected to the diode 14,
The ground is connected via the resistor R5 and the diode 12, and the electric charge is rapidly discharged. Since TR6 is turned off, an unintended current does not flow through the coil 13.

Thus, the positive electrode (+) in FIG. 8A is applied to the electrode a of the piezoelectric element 18 from the secondary side of the transformer 12.
Since a substantially trapezoidal pulse on the side is supplied, driving in a predetermined first direction can be performed.

Next, in the period T2, "H" of the signal Vb 'is supplied from the control section 16 to the base of the transistor TR3, the transistor TR3 is turned on, and the transistor TR7 is turned off, so that the switching circuit 17b is turned on. The electrode b of the piezoelectric element 18 is composed of a resistor R8, a diode 13, and a diode 1.
1 is grounded. "H" of the signal Vb is applied to the base of the transistor TR2 of the switching circuit 17a to turn on the transistor TR2 and turn off the transistor TR6.

When the period t2 has elapsed and the period t3 has started, the signal Va is supplied from the control section 16 to the base of the transistor TR1 of the switching circuit 14 during the period t3, and the switching circuit 14 is turned on / off (chopping operation). motion)
As a result, a back electromotive force is generated in the coil 13. The "L" of the signal Vb 'is supplied from the control unit 16 to the base of the transistor TR3, and the transistor TR3 is turned off and the transistor TR7 is turned on.
Back electromotive force is applied via 7 and stored.

After the elapse of the period t4, the signal Vb 'becomes "H", the transistor TR3 is turned on and the transistor TR7 is turned off, and the electric charge of the electrode b of the piezoelectric element 18 is changed to the diode 1
3. Discharged rapidly through resistor R8 and diode 11.

That is, in the period T1, a substantially trapezoidal pulse on the plus (+) side in FIG. 8A is supplied to the piezoelectric element 18, so that the driving in the predetermined first direction can be performed. In addition, in the period T2, since a substantially trapezoidal pulse on the minus (-) side in FIG. 8A is supplied to the piezoelectric element 18, the piezoelectric element 18 is driven in the opposite direction (second direction). It can be performed.

It goes without saying that the pulse generating circuit described above can be used by appropriately combining the circuit elements constituting the circuit according to the purpose.

[0070]

As described above, according to the pulse generator of the present invention, a high voltage sufficient to drive the electromechanical transducer can be obtained even with a low-voltage power supply such as a battery, and a complicated There is no need for a booster circuit having a configuration. Also, a circuit for generating a trapezoidal waveform pulse suitable for driving the electromechanical transducer can be constituted by a transformer or a coil and a switching circuit, and a control unit for controlling the control timing, and is smaller than a conventional pulse generator. A pulse generator with a small number of components and low power consumption can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a pulse generation circuit which is a basis of the present invention.

FIG. 2 is a pulse generation circuit diagram according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining an output pulse waveform and operation timing of the pulse generation circuit of FIG. 2;

FIG. 4 is a pulse generation circuit diagram according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating an output pulse waveform and operation timing of the pulse generation circuit of FIG. 4;

FIG. 6 is a circuit diagram specifically showing a configuration of the pulse generation circuit of FIG. 2;

FIG. 7 is a pulse generation circuit (part 1) in which the output polarity of the pulse generation circuit can be inverted.

FIG. 8 is a diagram for explaining an output pulse waveform and operation timing of the pulse generation circuit of FIG. 7;

FIG. 9 is a pulse generation circuit (part 2) in which the output polarity of the pulse generation circuit can be inverted.

FIG. 10 is a perspective view illustrating a configuration of a driving device using a piezoelectric element.

FIG. 11 is a diagram illustrating a waveform of a drive pulse applied to a piezoelectric element.

[Explanation of symbols]

 Reference Signs List 1 power supply 2 coil 3, 5 switch 4 piezoelectric element 11 power supply 12 transformer 13 coil 14, 17, 17a, 17b, 19 switching circuit 15 diode 16 control unit 18 piezoelectric element

Claims (8)

[Claims] An inductance element and a first switching means are connected in series to a power supply, and a capacitance is provided between a connection point between the inductance element and the first switching means and a connection point between the first switching means and the power supply. A pulse generating circuit that connects the second switching means in parallel with the capacitance element, and a control means, wherein the control means performs a chopping operation for intermittently turning on / off the first switching means. In addition, the back electromotive force generated in the inductance element is accumulated and accumulated in the capacitance element, and when the accumulated electric charge reaches a predetermined value, the second switching means is turned on to perform control. Pulse generator. 2. The pulse generator according to claim 1, wherein said inductance element is a coil. 3. The transformer according to claim 1, wherein the inductance element is a transformer.
The pulse generator according to claim 1, wherein the pulse generator is a secondary winding. 4. The pulse generator according to claim 1, wherein said capacitance element is an electromechanical transducer. 5. The pulse generator according to claim 1, wherein said capacitance element is a piezoelectric element. 6. The switching means according to claim 1, wherein said first switching means and said second switching means are switching means comprising semiconductor elements.
The pulse generator according to any one of the above. 7. The control means is constituted by a micro computer, performs a chopping operation for intermittently turning on / off the first switching means at a predetermined time interval, and accumulates and accumulates in the capacitance element. 2. The pulse generator according to claim 1, wherein whether or not the electric charge reaches a predetermined value is monitored, and when the electric charge reaches the predetermined value, control is performed so as to turn on the second switching means. 8. A pulse generator suitable for a driving mechanism for generating a telescopic displacement by applying a pulse voltage to an electromechanical transducer and driving a mechanism member by the generated displacement, comprising: an inductive circuit element and a first switching device. Means are connected in series to a power supply, and a capacitive electromechanical transducer is connected between a connection point between the inductive circuit element and the first switching circuit element and a connection point between the first switching means and the power supply. A pulse generating circuit in which a second switching means is connected in parallel to the capacitive electromechanical transducer; and a control means, wherein the control means intermittently turns on / off the first switching means. An operation is performed to accumulate back electromotive force generated in the inductive circuit element in the capacitive electromechanical transducer. When the accumulated electric charge reaches a predetermined value, the second switch is operated. A pulse generator for controlling the charging means to be turned on for discharging.