JP3539138B2 - Drive circuit for drive device using electromechanical transducer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a drive device using an electromechanical transducer, and more particularly, to a drive circuit of a drive device using an electromechanical transducer capable of obtaining a constant drive speed even when the temperature of the electromechanical transducer changes.
[0002]
[Prior art]
A driving member is coupled to the electromechanical transducer, and a sawtooth wave driving pulse is applied to the electromechanical transducer to reciprocate the driving member in the axial direction, and move the moving member frictionally coupled to the driving member in the axial direction. An actuating actuator (hereinafter referred to as an impact type actuator) is known.
[0003]
This type of impact-type actuator operates roughly as follows. First, at the gently rising portion of the sawtooth wave driving pulse applied to the electromechanical transducer, the electromechanical transducer is gently extended in the thickness direction and displaced, and the driving member coupled to the electromechanical transducer is also gently displaced in the positive direction. I do. At this time, the moving member is connected to the driving member by a frictional coupling force, and moves in the forward direction together with the driving member.
[0004]
Next, in the rapid falling portion of the sawtooth wave driving pulse applied to the electromechanical transducer, the electromechanical transducer rapidly shrinks and displaces in the thickness direction, and the driving member coupled to the electromechanical transducer also moves in the negative direction. Displaces rapidly. At this time, the moving member frictionally coupled to the driving member stays at that position by overcoming the frictional coupling force due to the inertial force and does not move. By continuously applying the sawtooth wave drive pulse to the electromechanical transducer, the moving member can be continuously moved in a predetermined direction.
[0005]
To move the moving member in the opposite direction, the waveform of the sawtooth drive pulse applied to the electromechanical transducer is changed, and a sawtooth drive pulse consisting of a rapid rising portion and a gentle falling portion is applied. Can be achieved.
[0006]
The movement of the driving member and the moving member frictionally coupled to the driving member is actually more complicated, and slippage occurs on the friction coupling surface both in the positive displacement and in the negative displacement of the driving member, and the driving is performed. It is considered that the member and the moving member move in the gentle displacement direction of the driving member as a whole while reciprocating while sliding.
[0007]
[Problems to be solved by the invention]
Generally, an electromechanical transducer such as a piezoelectric element has a characteristic that the capacitance increases when the temperature of the electromechanical transducer is high, and the capacitance decreases when the temperature is low.
[0008]
Due to this characteristic, when charging with a constant current in order to drive the electromechanical transducer, the higher the temperature of the electromechanical transducer, the higher the capacitance and the gentle rise of the sawtooth waveform of the drive pulse. The inclination angle θ becomes smaller. On the other hand, as the temperature of the electromechanical transducer is lower, the capacitance decreases and the inclination angle θ of the gentle rising portion of the sawtooth waveform of the drive pulse increases.
[0009]
That is, when the temperature greatly deviates from the reference temperature (for example, 25 ° C.), it is possible to obtain an optimal drive waveform (for example, a drive waveform set so as to have an optimal inclination angle θ based on the time at 25 ° C.). And the driving efficiency is reduced.
[0010]
As described above, in the drive device using the conventional electromechanical transducer, the drive speed fluctuates based on the temperature characteristics of the electromechanical transducer. Therefore, depending on the temperature of the environment in which the drive device is used, sufficient drive is required. There was an inconvenience that speed could not be obtained. An object of the present invention is to solve the above problems.
[0011]
[Means for Solving the Problems]
The present invention solves the above-mentioned problem, and the invention of claim 1 drives a driving member by supplying driving power to an electromechanical conversion element and causing the electromechanical conversion element to expand and contract. A driving circuit using an electromechanical transducer that moves a driven member frictionally coupled to the electromechanical transducer in a predetermined direction; a charging circuit that charges the electromechanical transducer with a constant current; A discharge circuit for discharging, a control circuit for switching the connection between the electromechanical transducer and the charging circuit and the discharge circuit at a predetermined timing to generate expansion and contraction displacement in the electromechanical transducer, and according to a change in environmental temperature. A current compensating circuit attached to the charging circuit for adjusting the amount of constant current supplied from the charging circuit to the electromechanical conversion element, regardless of changes in environmental temperature. And controlling the charging and discharging current to the electromechanical transducer as the displacement speed of the constant is obtained.
[0012]
The current compensation circuit is a current compensation circuit that compensates for a change in charging current based on a change in the capacitance of the electromechanical transducer due to a change in environmental temperature. And a resistor for changing the resistance value in accordance with the change of the charge current to compensate for the fluctuation of the charging current.
[0013]
According to a fourth aspect of the present invention, a driving member is driven by supplying driving power to the electromechanical conversion element and causing the electromechanical conversion element to expand and contract to move the driven member frictionally coupled to the driving member in a predetermined direction. In a drive circuit of a drive device using the electromechanical transducer to be moved, the drive circuit includes a current compensation circuit that compensates for a change in charging current based on a change in capacitance of the electromechanical transducer that fluctuates according to a change in environmental temperature, A first charging circuit that charges the electromechanical transducer with a constant current in which a change in environmental temperature is compensated, a first discharge circuit that discharges electric charge of the electromechanical transducer, and charges the electromechanical transducer A second charging circuit; and a current compensating circuit for compensating for a change in discharge current based on a change in capacitance of the electromechanical transducer that fluctuates in accordance with a change in environmental temperature. The change in environmental temperature is compensated. A second discharge circuit for discharging the electric charge of the electromechanical transducer with a constant current; and a predetermined timing for the first charge circuit and the first discharge circuit with respect to the electromechanical transducer according to the driving direction of the driving device. Or a control circuit for switching and connecting the second charging circuit and the second discharging circuit to the electromechanical transducer at a predetermined timing, so that a constant displacement is maintained regardless of a change in environmental temperature. The present invention is characterized in that the charging / discharging current to the electromechanical transducer is controlled so as to obtain a speed.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described. An embodiment of the present invention described below is an example in which a driving device using the electromechanical transducer of the present invention is applied to a photographing lens driving mechanism of a camera, and a piezoelectric element is used as the electromechanical transducer.
[0015]
FIG. 1 is a sectional view showing a configuration of a photographing lens driving mechanism of a camera suitable for applying the present invention. In FIG. 1, reference numeral 11 denotes a lens barrel, and a holding frame 12 for the first lens L1 is fixedly attached to the left end thereof, and a right end 11a thereof forms a holding frame for the third lens L3. Inside the lens barrel 11, a lens holding frame 13 of the second lens L2 is disposed so as to be movable in the optical axis direction. A drive shaft 14 drives the lens holding frame 13 in the optical axis direction. The drive shaft 14 is movable in the optical axis direction by the first flange portion 11b of the lens barrel 11 and the flange portion 12b of the lens holding frame 12. , One end of which is bonded and fixed to one surface of the piezoelectric element 15.
[0016]
The piezoelectric element 15 is displaced in the thickness direction to displace the drive shaft 14 in the axial direction. One end surface of the piezoelectric element 15 is adhered and fixed to the drive shaft 14, and the other end surface is attached to the second flange portion 11 c of the lens barrel 11. Adhesively fixed.
[0017]
The lens holding frame 13 for holding the second lens L2 has a slider block 13b which is a moving member extending upward. A drive shaft 14 extends through the slider block 13b in the lateral direction. An opening 13c is formed in an upper portion of the slider block 13b through which the drive shaft 14 passes, and an upper half of the drive shaft 14 is exposed. A pad 16 which is in contact with the upper half of the drive shaft 14 is fitted into the opening 13c, and a projection 16a is provided on the upper portion of the pad 16. The projection 16a of the pad 16 is pushed down by a leaf spring 17. The pad 16 is provided with a downward biasing force F which comes into contact with the drive shaft 14. FIG. 2 is a cross-sectional view showing a configuration of a frictional coupling portion between the drive shaft 14, the slider block 13b, and the pad 16.
[0018]
Reference numeral 18 denotes a guide shaft that prevents the lens holding frame 13 from swinging and guides the lens holding frame 13 to move along the optical axis. Reference numeral 37 denotes a lens position detection sensor that detects the position of the lens L2. Can be detected to determine the lens position.
[0019]
Next, the control operation will be described. When the movement of the lens L2 in the direction of the arrow a is required, a driving pulse having a sawtooth waveform composed of a gentle rising portion as shown in FIG. .
[0020]
At the gentle rising portion of the drive pulse, the piezoelectric element 15 gradually expands in the thickness direction, and the drive shaft 14 is axially displaced in the direction of arrow a. Therefore, the slider block 13b and the pad 16, which are urged by the leaf spring 17 and are frictionally coupled to the drive shaft 14, also move in the direction of arrow a, so that the lens holding frame 13 can be moved in the direction of arrow a.
[0021]
At the rapid falling portion of the drive pulse, the piezoelectric element 15 rapidly contracts in the thickness direction, and the drive shaft 14 is also displaced in the axial direction in the direction opposite to the arrow a. At this time, the slider block 13b, the pad 16 and the lens holding frame 13, which are urged against the drive shaft 14 by the leaf spring 17 and pressed against it, substantially overcome the frictional coupling force between the drive shaft 14 and the drive shaft 14 due to its inertia. Lens holding frame 13 does not move.
[0022]
The term “substantially” as used herein means that the slider block 13 b and the friction coupling surface between the pad 16 and the drive shaft 14 follow and slide in both directions of the arrow a and the opposite direction. This means that the movement in the direction of the arrow a as a whole due to the time difference is also included.
[0023]
By continuously applying the drive pulse having the above-described waveform to the piezoelectric element 15, the lens holding frame 13 can be continuously moved in the direction indicated by the arrow a.
[0024]
The movement of the lens holding frame 13 in the direction opposite to the arrow a can be achieved by applying to the piezoelectric element 15 a drive pulse having a waveform consisting of a rapid rising portion followed by a gentle falling portion.
[0025]
FIG. 4 is a block diagram of a driving circuit of the piezoelectric element. The drive circuit 30 drives the piezoelectric element 15 by charging and discharging with two kinds of currents 1 and 2 (current 1> current 2) having different current values. The driving circuit 30 drives the piezoelectric element 15 with two kinds of currents having different current values. Thereby, the piezoelectric element 15 can be expanded and contracted at different speeds.
[0026]
The driving circuit 30 includes a control circuit 31, an input device 32 for inputting a target position when the lens L2 is moved, a current 1 charging circuit 33, a current 1 discharging circuit 34, a current 2 charging circuit 35, a current 2 discharging circuit 36, and It comprises a lens position detection sensor 37 for detecting the position of the lens L2, that is, the current position of the lens holding frame 13.
[0027]
The input device 32 corresponds to, for example, a rotation angle detector of a zoom operation ring when the lens L1 is moved by a zoom operation in a zoom lens. The lens position detection sensor 37 detects the position of the lens holding frame 13, and is provided on the lens holding frame 13 such as a magnetized rod arranged parallel to the drive shaft 14 and a magnetized rod. A known position detector including a magnetoresistive element for detecting the magnetism of the magnetized rod can be used. The magnetizing rod can also be used as a guide shaft 18 for guiding the lens holding frame 13.
[0028]
The control circuit 31 calculates the moving direction and the moving distance of the lens based on the signals input from the input device 32 and the lens position detection sensor 37, determines the charging circuit and the discharging circuit to be used, and determines the current 1 charging circuit 33, It outputs PWM signals (pulse width modulation signals) PWM1, PWM2, PWM3, and PWM4 for setting the current 1 discharge circuit 34, the current 2 charge circuit 35, and the current 2 discharge circuit 36 to be activated or deactivated.
[0029]
FIG. 5 is a diagram showing a circuit configuration of the current 1 charging circuit 33, the current 1 discharging circuit 34, the current 2 charging circuit 35, and the current 2 discharging circuit 36.
[0030]
The current 1 charging circuit 33 is a circuit for rapidly charging the piezoelectric element 15 with a large current. When the current 1 charging circuit 33 operates, the piezoelectric element 15 rapidly expands and displaces. The current 1 discharge circuit 34 rapidly discharges the electric charge of the piezoelectric element 15 with a large current. When the current 1 discharge circuit 34 operates, the piezoelectric element 15 is rapidly contracted and displaced.
[0031]
The current 2 charging circuit 35 is a constant current charging circuit having a smaller current than the current 1 charging circuit 33, and charges the piezoelectric element 15 gradually. Therefore, when the current 2 charging circuit 35 is activated, the piezoelectric element 15 is gradually discharged. Causes an elongation displacement. The current 2 discharge circuit 36 is a constant current discharge circuit having a smaller current than the current 1 discharge circuit 34 and gradually discharges the electric charge of the piezoelectric element 15. Therefore, when the current 2 discharge circuit 36 operates, the piezoelectric element 15 is gradually discharged. Causes contraction displacement.
[0032]
The current 2 charging circuit 35 is a constant current charging circuit, and the current 2 discharging circuit 36 is a constant current discharging circuit, as is clear from the driving principle, when the piezoelectric element 15 is gradually extended or contracted. This is because the moving member can be moved faster if the moving member is displaced at a constant speed.
[0033]
A current compensating thermistor TH1 for compensating for the temperature characteristic of the piezoelectric element is inserted into the current 2 charging circuit 35, and the transistor TR1 is also activated by the fluctuation of the capacitance of the piezoelectric element 15 caused by the fluctuation of the environmental temperature. It is configured to compensate for fluctuations in charging current when the piezoelectric element 15 is charged with a constant current through the same. The thermistor TH1 for temperature compensation is connected in parallel to the resistor R1 for determining the constant current value, but may be connected in series to the resistor R1.
[0034]
A temperature compensating thermistor TH2 for compensating for the temperature characteristics of the piezoelectric element is also inserted in the current 2 discharging circuit 36, and the piezoelectric element 15 is also supplied with a voltage via the transistor TR3 due to a change in capacitance of the piezoelectric element 15 caused by a change in environmental temperature. It is configured to compensate for a variation in the discharge current when the charge of the element 15 is discharged with a constant current.
[0035]
FIG. 6 is a timing chart for explaining the operation timing of the charging / discharging circuit in the feeding operation for moving the lens L2 in the direction of the arrow a. FIG. 5 is a timing chart for explaining the operation timing of the discharge circuit. Hereinafter, the driving operation of the driving circuit 30 will be described with reference to the timing charts of FIGS. 1, 5, 6, and 7.
[0036]
First, a description will be given of the case of the extending operation in which the lens L2 is moved in the direction of arrow a (see FIG. 1).
[0037]
In this case, the control circuit 31 calculates the moving direction and the moving distance of the lens based on the signals input from the input device 32 and the lens position detection sensor 37 as described above, and determines the charging circuit and the discharging circuit to be used. Then, a PWM1 signal as shown in FIG. 6A is output to the current 2 charging circuit 35, and a PWM2 signal as shown in FIG. 6B is output to the current 1 discharging circuit 34. In addition, as shown in FIGS. 6C and 6D, the PWM3 signal is turned off and the PWM4 signal is turned off as shown in FIGS. 6C and 6D, and the current 1 charging circuit 33 and the current 2 discharging circuit 36 are set to be inactive. .
[0038]
In the current 2 charging circuit 35, when the PWM1 signal goes to "H" level, the transistor TR5 is turned on, TR2 and TR1 start operating, and a charging current flows to the piezoelectric element 15 via the resistor R1 and the thermistors TH1 and TR1. The electric charge is charged in the piezoelectric element 15. The current flowing through TR1 is determined by the base-emitter voltage Vbe of TR2 and the combined resistance R of the resistor R1 and the thermistor TH1, and the charging current value i for charging the piezoelectric element 15 is given by the following equation (1). Is the value represented by
[0039]
i = Vbe / R (1)
However, Vbe = 0.6V, R = (R1.TH1) / (R1 + TH1)
When the PWM1 signal goes to "L" level, charging by the current 2 charging circuit 35 is stopped, and at the same time, the PWM2 signal goes to "H" level, and the field effect transistor FET2 of the current 1 discharging circuit 34 turns on. Since a MOS-FET is used for the FET2, the internal resistance when it is on is small and substantially short-circuited, so that the electric charge charged in the piezoelectric element is rapidly discharged through the FET2.
[0040]
Note that the capacitor C1 of the current 2 charging circuit 35 has a function of accelerating the change time of the switching when the transistor TR5 is turned on / off, so that it is necessary to substantially provide an off section when switching the PWM1 signal and the PWM2 signal on / off. Therefore, the setting of the timing of the PWM signal in the control circuit 31 becomes easy. The capacitor C2 of the current 1 charging circuit 33 is exactly the same, and has a function of accelerating the change time of switching when the transistor TR6 is turned on / off.
[0041]
By the above operation, a drive pulse having a gentle rising portion and a rapid falling portion as shown in FIG. 6E is applied to the piezoelectric element 15, and the piezoelectric element 15 gradually expands in the direction of arrow a. Displacement and a rapid contraction displacement in the direction opposite to the arrow a occur, and a feeding operation of moving the lens L2 in the direction of the arrow a (see FIG. 1) via the drive shaft 14 and the slider block 13b can be performed.
[0042]
Next, a description will be given of the case of a retraction operation for moving the lens L1 in the direction opposite to the arrow a (see FIG. 1).
[0043]
In this case, the control circuit 31 outputs a PWM3 signal as shown in FIG. 7C to the current 1 charging circuit 33 and a PWM4 signal as shown in FIG. 7D to the current 2 discharging circuit 36. Output. In addition, as shown in FIGS. 7A and 7B, the PWM1 signal is turned off and the PWM2 signal is turned off as shown in FIGS. 7A and 7B, and the current 2 charging circuit 35 and the current 1 discharging circuit 34 are set to be inactive. .
[0044]
In the current 1 charging circuit 33, when the PWM3 signal becomes "H" level, the transistor TR6 is turned on, and the FET1 is turned on. Since the internal resistance of the FET 1 is small, the piezoelectric element 15 is connected to the power supply via the FET 1 and is charged rapidly.
[0045]
When the PWM3 signal becomes "L" level, the transistor TR6 is turned off, the FET1 is also turned off, and charging by the current 1 charging circuit 33 is stopped. At the same time, the PWM4 signal becomes "H" level, the transistor TR3 of the current 2 discharging circuit 36 is turned on, and the electric charge charged in the piezoelectric element 15 is gradually discharged through the resistor R3 and the thermistor TH2.
[0046]
By the above operation, a drive pulse having a rapid rising portion and a gentle falling portion as shown in FIG. 7E is applied to the piezoelectric element 15, and the piezoelectric element 15 has a gentle driving direction opposite to the arrow a. A slight contraction displacement and a rapid extension displacement in the direction of arrow a occur, and a retraction operation of moving lens L2 in the direction opposite to arrow a (see FIG. 1) via drive shaft 14 and slider block 13b can be performed. .
[0047]
FIG. 8 is a diagram showing the temperature characteristics of the capacitance of the piezoelectric element. As is clear from this figure, the capacitance of the piezoelectric element increases in proportion to the rise in temperature.
[0048]
FIG. 10 is a diagram showing the relationship between the charging time and the temperature of the piezoelectric element, and FIG. 11 is a diagram showing the relationship between the inclination angle of the drive waveform for charging the piezoelectric element and the temperature. As shown in FIG. 2 shows data on the relationship between the time T1 for charging up to 30 V and the temperature and the relationship between the inclination angle .theta. Of the drive waveform and the temperature.
[0049]
In FIG. 10, which shows the relationship between the charging time and the temperature of the piezoelectric element, the line (a) shows the case where the temperature compensation by the thermistor is not performed. This indicates that the charging time becomes longer because the capacitance increases. Line (b) shows the case where temperature compensation is performed by a thermistor, and the charging time is not affected by the temperature, and charging is performed in a substantially constant time.
[0050]
In FIG. 11 showing the relationship between the inclination angle of the driving waveform for charging the piezoelectric element and the temperature, the line (a) shows the case where the temperature compensation by the thermistor is not performed, and the charging time becomes longer as the temperature is higher. Therefore, the inclination angle θ becomes small, and it becomes difficult to charge the battery to a predetermined voltage, which indicates that the driving force decreases and the driving speed decreases. In addition, the lower the temperature, the shorter the charging time, the greater the inclination angle θ, the gentler rising waveform of the drive pulse gradually changes to a faster rising waveform, and the difference in the expansion / contraction speed of the piezoelectric element becomes smaller. Indicates that the driving speed decreases.
[0051]
The line (b) in FIG. 11 shows the case where the temperature compensation is performed by the thermistor. The inclination angle θ of the drive waveform is kept almost constant without being affected by the temperature, and the drive speed is reduced by the temperature change. It is not shown.
[0052]
【The invention's effect】
As described above, since the drive circuit of the drive device using the electromechanical transducer of the present invention can compensate for the fluctuation of the drive speed based on the temperature characteristics of the electromechanical transducer, the environmental temperature at which the drive device is used can be compensated. , The driving speed can always be obtained sufficiently, and the applicable range of the driving device can be expanded.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a configuration of a photographing lens driving mechanism of a camera.
FIG. 2 is a sectional view showing a configuration of a frictional coupling portion between a drive shaft of the lens drive mechanism shown in FIG. 1, a slider block and a pad.
FIG. 3 illustrates a waveform of a driving pulse.
FIG. 4 is a block diagram of a driving circuit.
FIG. 5 is a diagram showing a circuit configuration of a current 1 charging circuit, a current 1 discharging circuit, a current 2 charging circuit, and a current 2 discharging circuit.
FIG. 6 is a timing chart (part 1) for explaining the operation timing of the charge / discharge circuit.
FIG. 7 is a timing chart for explaining the operation timing of the charge / discharge circuit (part 2).
FIG. 8 is a diagram illustrating temperature characteristics of capacitance of a piezoelectric element.
FIG. 9 is a diagram illustrating a charging time of a piezoelectric element and an inclination angle of a driving waveform.
FIG. 10 is a diagram showing a relationship between charging time and temperature of a piezoelectric element.
FIG. 11 is a diagram showing a relationship between a tilt angle of a driving waveform for charging a piezoelectric element and temperature.
[Explanation of symbols]
Reference Signs List 11 lens barrel 13 second lens lens holding frame 13b slider block 14 drive shaft 15 piezoelectric element 30 drive circuit 31 control circuit 32 input device 33 current 1 charge circuit 34 current 1 discharge circuit 35 current 2 charge circuit 36 current 2 discharge circuit 37 Lens position detecting sensors FET1, FET2 Field effect transistors TR1, TR2, TR3, TR4, TR5, TR6 Transistors TH1, TH2 Thermistor

Claims (4)

An electromechanical conversion element that supplies driving power to the electromechanical conversion element, drives a driving member by generating expansion and contraction displacement in the electromechanical conversion element, and moves a driven member frictionally coupled to the driving member in a predetermined direction. In the drive circuit of the drive device used,
A charging circuit that charges the electromechanical transducer with a constant current;
A discharge circuit that discharges the charge of the electromechanical conversion element,
A control circuit that switches the connection between the electromechanical transducer and the charging circuit and the discharge circuit at a predetermined timing to generate expansion and contraction displacement in the electromechanical transducer,
A current compensating circuit attached to the charging circuit that adjusts the amount of a constant current supplied from the charging circuit to the electromechanical transducer in accordance with a change in the environmental temperature; A drive circuit of a drive device using an electromechanical transducer, wherein the drive circuit controls a charge / discharge current to the electromechanical transducer so as to obtain a displacement speed. 2. The electromechanical transducer according to claim 1, wherein the current compensating circuit is a current compensating circuit that compensates for a change in charging current based on a change in capacitance of the electromechanical transducer due to a change in environmental temperature. Drive circuit of the driving device. The driving device using the electromechanical transducer according to claim 2, wherein the current compensation circuit includes a resistor whose resistance value changes in accordance with a change in environmental temperature to compensate for a change in charging current. Drive circuit. An electromechanical conversion element that supplies driving power to the electromechanical conversion element, drives a driving member by generating expansion and contraction displacement in the electromechanical conversion element, and moves a driven member frictionally coupled to the driving member in a predetermined direction. In the drive circuit of the drive device used,
Equipped with a current compensation circuit that compensates for fluctuations in charging current based on fluctuations in the capacitance of the electromechanical transducer that fluctuate in response to changes in environmental temperature. A first charging circuit for charging;
A first discharge circuit that discharges the charge of the electromechanical conversion element;
A second charging circuit that charges the electromechanical conversion element;
A current compensation circuit that compensates for a change in discharge current based on a change in the capacitance of the electromechanical transducer that fluctuates in accordance with a change in environmental temperature is provided. A second discharging circuit for discharging the electric charge,
The first charging circuit and the first discharging circuit are switched and connected to the electromechanical transducer at a predetermined timing according to the driving direction of the driving device, or the second charging circuit and the second discharging circuit are connected to each other. A control circuit that switches and connects to the electromechanical transducer at a predetermined timing, and controls a charging / discharging current to the electromechanical transducer so that a constant displacement speed is always obtained regardless of a change in environmental temperature. A drive circuit of a drive device using an electromechanical transducer, characterized in that:

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