JP3140236B2 - Ultrasonic motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor driving circuit, and more particularly to an ultrasonic motor driving circuit for optimally driving an ultrasonic motor.

[0002]

2. Description of the Related Art Various ultrasonic motor drive circuits for optimally driving an ultrasonic motor have been known. For example, Japanese Patent Application Laid-Open No. 63-262070 discloses a DC power supply using an inductive element such as a transformer. Technical means for switching and generating an AC signal by the induced electromotive force are disclosed.

On the other hand, in a device such as a camera which uses a battery as a power supply, it is known that a power supply voltage fluctuates depending on a degree of consumption of the battery or a use environment. Therefore, in these devices, the operable power supply voltage has a certain width, and for example, in the case of a device using a battery of 6 V as a power supply, the operable voltage range (operation guarantee range) of the device itself is set. Many are set to about 6V to 3.5V.

[0004]

When the technical means disclosed in Japanese Patent Application Laid-Open No. 63-262070 is used, that is, a high voltage AC signal is generated from a low voltage source and applied to the ultrasonic motor. In the case of using the technical means to perform the above, in consideration of the above points, even if the voltage of the battery as the power supply voltage reaches the lowest voltage in the operation guarantee range, the constants such as the turns ratio of the transformer are set so as to obtain a predetermined torque. Must be set.

However, when the ultrasonic motor to which the technical means is applied requires high-speed rotation, it is necessary to use a frequency close to the resonance point as the drive frequency.

As described above, if the constant of the inductive element is set so that the battery can operate even when the voltage of the battery is the lowest voltage in the operation guarantee range, the voltage of the battery is the highest voltage in the operation guarantee range. Is the optimal drive frequency (resonance frequency)
In such a case, there is a possibility that the input power becomes too large and an abnormal noise is generated from the ultrasonic motor.

As a countermeasure against the abnormal noise, it is conceivable to provide a constant voltage means for the power supply voltage. However, providing a new circuit is not preferable because it leads to an increase in the size of the device itself and an increase in cost. On the other hand, when not used near the optimum driving frequency, there is a possibility that a sufficient torque and rotation speed cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a small and low-cost ultrasonic wave capable of obtaining a sufficient mechanical output without causing an abnormal state even when a power supply voltage largely fluctuates. It is an object to provide a motor drive circuit.

[0009]

According to a first aspect of the ultrasonic motor driving circuit according to the present invention for achieving the above object, a DC
The current flowing through the coil connected to the power supply is
Based on the induced electromotive force generated when switching
And generates an AC signal based on the AC signal.
A voltage detecting means for detecting a voltage of the DC power supply in an ultrasonic motor driving circuit for driving an ultrasonic motor by applying the voltage to an electro-mechanical energy conversion element ;
Pulse width setting means for setting a pulse width of a switching pulse in accordance with the voltage detected by the voltage detecting means ; monitoring means for detecting a driving state of the ultrasonic motor; and AC power based on an output of the monitoring means. Frequency control means for controlling the frequency of the signal .
You.

In order to achieve the above object, a second ultrasonic motor drive circuit according to the present invention is connected to a DC power supply.
Current flowing through the switched coil is switched by the switching element.
AC based on induced electromotive force generated during switching
Generating an electric signal, and converting the AC signal into an electric motor of an ultrasonic motor.
Driving the ultrasonic motor by applying the energy conversion element, the ultrasonic motor driving circuit, and a voltage detecting means for detecting the voltage of the DC power supply, the voltage detection hand
Pulse width range setting means for setting the pulse width range of the switching pulse in accordance with the voltage detected by the stage ; monitor means for detecting the driving state of the ultrasonic motor; and the pulse based on the output of the monitor means. Width is above pulse width
This equipped with pulse width control means, the controlling in the range of
And features.

[0011]

[0012]

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an electric circuit diagram of an ultrasonic motor driving circuit showing a first embodiment of the present invention.

The ultrasonic motor driving circuit according to the first embodiment comprises two driving electrodes 10A and 10B and a monitor electrode 1.
A predetermined two-phase AC signal is applied to a known ultrasonic motor 10 having 0M, and a monitor signal from the monitor electrode 10M is monitored to control the driving of the ultrasonic motor 10.

That is, the driving circuit comprises a CPU 1 for controlling the driving circuit, a starting frequency fs of an AC signal applied to the ultrasonic motor 10, and a voltage-corresponding pulse width Wn.
A oscillating circuit 3 for generating and outputting a pulse signal φORG having a frequency approximately four times that of an AC signal applied to the ultrasonic motor 10 under the control of the CPU 1, A pulse width setting circuit 4 for defining the pulse width of the pulse signal φORG output from the oscillation circuit 3 and outputting the pulse signal as a pulse signal φUSR, and converting the pulse signal φUSR output from the pulse width setting circuit 4 into four A pulse conversion circuit 5 that divides and outputs the phase pulse signals φ1 to φ4, and switching transistors Q1 to Q4 that perform switching operations corresponding to the pulse signals φ1 to φ4 output from the pulse conversion circuit 5, respectively. The positive voltage of the DC power supply 7 is supplied to the intermediate tap on the primary side, and the switching transistor Q1
And the switching operation of Q2, the primary side is turned on, and accordingly, the transformer T1 that outputs the A-phase AC signal VA to the secondary side, and the primary side is also turned on by the switching operation of the switching transistors Q3 and Q4. A transformer T2 for outputting a B-phase AC signal VB to the next side; a waveform shaping circuit 9 for converting a monitor signal from the monitor electrode 10M of the ultrasonic motor 10 into a predetermined digital signal; An output signal and a pulse signal φ which is one output from the pulse conversion circuit 5
1 and the phases of the two signals are compared and counted. As a result, the phase difference counter 8 for sending the phase difference between the phases of the two signals to the CPU 1 and the ultrasonic motor 10 Generates a predetermined pulse by detecting the rotation of
A rotary encoder 11 for sending to the CPU 1;
The positive voltage of the C power supply 7 is detected, and the detection result
A main part is constituted by the DC voltage detection circuit 6 to be sent to the PU 1.

The ultrasonic motor 10 is a known traveling wave ultrasonic motor having a piezoelectric element, and has the two electrodes 10A and 10B as described above. That is, the two-phase (A-phase and B-phase) AC signals VA and VB whose phases are shifted from each other by about 90 ° are applied to the electrodes 10A and 10B. Is driven to rotate. The ultrasonic motor 10 has a monitor electrode 10M, and an output signal (monitor signal) VM from the monitor electrode 10M is input to the waveform shaping circuit 9 as described above.

FIG. 2 is a circuit diagram of the oscillation circuit 3 of the first embodiment.
FIG. 2 is an electric circuit diagram showing a configuration of a pulse width setting circuit 4 and a pulse conversion circuit 5.

The oscillating circuit 3 receives a clock from the oscillator 33 and a latch 31 for latching a predetermined output from the CPU 1, and receives the clock from the oscillator 33 and outputs the ultrasonic motor 1 based on the output of the latch 31.
And a down counter 32 for generating and outputting a pulse signal φORG having a frequency approximately four times as high as the AC signal applied to 0. The output of the down counter 32 has a pulse width P32 = 1/4 as shown in the timing chart of FIG.
It has a pulse waveform having f (f is the frequency of the AC signal applied to the ultrasonic motor 10).

The above-mentioned pulse width setting circuit 4 is similarly provided with C
A latch 41 for latching a predetermined output from PU1 and a clock received from the oscillator 33, and outputs an output of the down counter 32 based on the output of the latch 41, that is, a signal for limiting the pulse width of the pulse signal φORG. A pulse signal φU having a pulse width (see pulse width P42 in FIG. 4) set by the down counter 42, the pulse signal φORG, and an output signal from the down counter 42.
RS flip-flop 4 for outputting SR (see FIG. 4)
And 3.

Further, the pulse conversion circuit 5 has a 4-bit shift register composed of four D flip-flops 51, and divides the pulse signal φUSR into four-phase pulse signals φ1 to φ4 (FIG. 4) Output to the switching transistors Q1 to Q4, respectively.

FIG. 3 is an electric circuit diagram showing the phase difference counter 8 and the waveform shaping circuit 9 in the first embodiment.

The waveform shaping circuit 9 includes a pressure reducing resistor 94,
95, a clamp diode 92, 93 and an inverter 91 having hysteresis. The input end of the resistor 94 is connected to the monitor electrode 10M for detecting a vibration state provided on the ultrasonic motor 10, so that the monitor signal VM from the ultrasonic motor 10 is subjected to the waveform shaping. The signal is input to the circuit 9. The monitor signal VM (see FIG. 4) input to the waveform shaping circuit 9 is decompressed by the decompression resistors 94 and 95, rectified by the clamp diodes 92 and 93, and further shaped into a digital signal by the inverter 91. (See FIG. 4) and output to the phase difference counter 8.

The phase difference counter 8 calculates a phase difference between an output signal from the waveform shaping circuit 9, that is, a waveform-shaped monitor signal VM and a pulse signal φ 1 which is one output from the pulse converting circuit 5. Upon receiving an RS flip-flop 81 to be detected and a clock from the oscillator 33,
An up-counter 82 counts the output from the RS flip-flop 81, that is, the phase difference between the monitor signal VM and the pulse signal φ2, and outputs the result to the oscillation circuit 3 in the CPU 1.

The rotary encoder 10 detects a rotation state of the ultrasonic motor 10 and outputs a predetermined pulse, and can be constituted by a known photo interrupter, MR sensor, or the like. The output is sent to the CPU 1.

Next, the operation of the ultrasonic motor driving circuit according to the first embodiment will be described with reference to the flowchart shown in FIG.

First, after starting (step S1), DC
The positive DC voltage of the power supply 7 is detected by the DC voltage detection circuit 6 (step S2). Next, the DC voltage corresponding to the drive frequency fs at the time of startup written in the memory 2 and the DC voltage detected in the above step S2. The pulse width Wn of the switching pulse is read (step S3).

Here, the driving frequency fs is inspected after assembling for each ultrasonic motor, and the optimum value is written in the memory 2. On the other hand, the pulse width Wn of the switching pulse is selectively stored in the memory 2 as shown in FIG. To be read.

In this embodiment, the power supply voltage is 3.5 V
It is assumed that the device guarantees the operation within the range of ~ 6V. When the power supply voltage is 3.5V, the pulse width of the switching pulse is maximized (the width of the pulse signals φ1 to φ4 is about 1 / (Four cycles), a predetermined output is issued. This is because the primary windings of transformers T1 and T2 and 2
This can be realized by setting the ratio of the secondary winding to a value corresponding to the power supply voltage of 3.5V. For example, if the ultrasonic motor 10 requires a voltage of ± 70 VP-P, the winding ratio should be about 1: 2
It may be set to 0.

The frequency fs and the pulse width Wn thus read are written in the latches 31 and 41 of the oscillation circuit 3 and the pulse width setting circuit 4, respectively (step S4). Then, the ultrasonic motor 10 is started at the frequency fs with the switching pulse width fixed at Wn (step S5).

Thereafter, the monitor electrode 1 of the ultrasonic motor 10
Monitor signal VM from 0M and 1 from pulse conversion circuit 5
By comparing the phase with the pulse signal φ1 as an output, the phase difference is read out from the phase difference counter 8 (step S6),
The ultrasonic motor is driven at the optimum frequency fr by changing the frequency so that the value becomes a predetermined value (step S7, step S8, step S9).

Then, the rotational state of the ultrasonic motor 10 is detected by the rotary encoder 11, and when the ultrasonic motor 10 rotates by a predetermined number of pulses, the motor 10 is stopped (steps S10 and S11). These controls and the like are performed by the CPU 1.

According to the first embodiment, even if the ultrasonic motor is driven in the vicinity of the high output and high efficiency resonance point fr, no abnormal noise is generated, and sufficient torque can be obtained regardless of the DC voltage. The rotation speed can be obtained.

Next, an ultrasonic motor driving circuit according to a second embodiment of the present invention will be described.

The second embodiment has the same circuit configuration as that of the first embodiment, and differs only in the control operation of the CPU 1. Only the operation will be described with reference to the flowchart shown in FIG. However, other descriptions are omitted. In the second embodiment, a constant speed rotation is obtained by changing the frequency.

First, after the start (step S21), D
The positive DC voltage of the C power supply 7 is detected by the DC voltage detection circuit 6 (step S22). Next, the drive frequency fs at the time of startup written in the memory 2 and the above-described step S22
The pulse width Wn of the switching pulse corresponding to the DC voltage detected in is read out (step S23).

Here, the drive frequency fs is inspected after assembling for each ultrasonic motor, and the optimum value is written in the memory 2 as in the first embodiment. On the other hand, as for the pulse width Wn of the switching pulse, the pulse width at which noise starts to be generated when the voltage is driven at the optimum frequency fr for each voltage is stored in the memory 2 and read out selectively. ing.

Also, in the second embodiment, as in the first embodiment, it is assumed that the device guarantees the operation within the power supply voltage range of 3.5 V to 6 V. In this case, a predetermined output is generated by maximizing the pulse width of the switching pulse (the width of the pulse signals φ1 to φ4 is about 周期 cycle).

The frequency fs and the pulse width Wn thus read are written in the latches 31 and 41 of the oscillation circuit 3 and the pulse width setting circuit 4, respectively (step S24), and the ultrasonic motor 10 sets the switching pulse width to Wn. At the frequency fs (step S25).

Thereafter, the rotational state of the ultrasonic motor 10 is detected by the rotary encoder 11 and the rotational encoder 11
The speed is calculated by monitoring the pulse signal from the CPU (step S26), and the frequency is increased or decreased by comparing with the target rotation speed (step S27, step S28, step S2).
9). That is, as shown in FIG.
When a frequency higher than r is used, the frequency is decreased to increase the speed, and is increased to reduce the speed.

In the second embodiment, the ultrasonic motor 10
It is also possible to monitor the phase of the monitor signal VM from the monitor electrode 10M and control the frequency so as not to be higher than the optimum driving frequency fr.

According to the second embodiment, since the pulse width of the switching pulse is defined by Wn, even when the driving frequency is controlled to change the rotation speed of the ultrasonic motor, abnormal noise is generated. And the speed can be controlled in a wide range including the resonance point.

Next, an ultrasonic motor driving circuit according to a third embodiment of the present invention will be described.

The third embodiment has the same circuit configuration as that of the first embodiment and differs only in the control operation of the CPU 1. Therefore, only the operation will be described with reference to the flowchart shown in FIG. However, other descriptions are omitted.

First, after the start (step S31), the positive DC voltage of the DC power supply 7 is detected by the DC voltage detection circuit 6 as in the first embodiment (step S32). Next, the drive frequency fs at the time of startup written in the memory 2
Then, the pulse width Wn of the switching pulse corresponding to the DC voltage detected in step S32 and the lower limit value Wn 'of the pulse width are read (step S33).

By utilizing the lower limit value Wn 'of the pulse width, the pulse width Wn and the lower limit value Wn' of the pulse width are used to define the allowable use range of the pulse width by the DC voltage detected in step S32. be able to. Thus, the third embodiment controls the rotation speed of the ultrasonic motor 10 in the same manner as the second embodiment, but the drive frequency follows a more efficient optimum frequency fr, and the pulse width is increased. Can be changed to control the speed.

The drive frequency fs is inspected after assembling for each ultrasonic motor, and the optimum value is written in the memory 2 as in the first embodiment. On the other hand, the pulse width Wn of the switching pulse and the lower limit value Wn ′ of the pulse width are similarly stored in the memory 2 and selectively read.

Also, in the third embodiment, as in the first and second embodiments, it is assumed that the device guarantees operation within a power supply voltage range of 3.5 V to 6 V. When the voltage is 0.5 V, a predetermined output is generated by maximizing the pulse width of the switching pulse (the width of the pulse signals φ1 to φ4 is about 周期 cycle).

The frequency fs and the pulse width Wn thus read are written in the latches 31 and 41 of the oscillation circuit 3 and the pulse width setting circuit 4, respectively (step S34), and the ultrasonic motor 10 sets the switching pulse width to Wn. At the frequency fs (step S35).

Thereafter, as in the first embodiment, the phase of the monitor signal VM from the monitor electrode 10M is compared with the phase of the pulse signal φ1 which is one output from the pulse conversion circuit 5, and the phase difference is compared with the phase difference counter. 8 (Step S3)
6). Then, the frequency is changed so that the value becomes a predetermined value (step S37, step S8, step S9), and the ultrasonic motor is driven at the optimum frequency fr.

Next, the rotation speed of the ultrasonic motor 10 is detected by the rotary encoder 11 (step S40), and it is determined whether or not the detection result is higher than the target speed (step S40).
41) The pulse width is raised or lowered within the range of the above-mentioned pulse width Wn and the lower limit value Wn 'of the pulse width (step S42, step S43, step S44, step S45).

According to the third embodiment, as in the second embodiment, the speed can be adjusted without generating abnormal noise, and the lower limit value of the pulse width is specified by the voltage. Thus, it is possible to prevent a problem that the ultrasonic motor is stopped because the pulse width is too low. In particular, when the contact interface is made of an inorganic material, it is possible to stably control the low-speed side of the pulse width even if the material is hard.

Next, an ultrasonic motor driving circuit according to a fourth embodiment of the present invention will be described.

FIG. 10 is an electric circuit diagram showing an ultrasonic motor driving circuit according to the fourth embodiment.

In the fourth embodiment, the ultrasonic motor drive circuit of the present invention is applied to a camera system of an interchangeable lens type.

Generally, since a camera system has a built-in power supply in a camera body, the built-in power supply is often used as a driving source of an ultrasonic motor for a photographing optical system. In the present embodiment, the DC power source 7, the DC voltage detection circuit 6, the oscillation circuit 3, the pulse conversion circuit 4, etc. of the ultrasonic motor drive circuit of the first embodiment are a camera body unit (indicated by BY in the drawing). The other components are arranged in a lens unit (indicated by LY in the figure).
Since the components denoted by the same reference numerals as those in the first embodiment have the same configuration and operation, the description is omitted here.

The camera body unit BY and the lens unit LY have built-in control CPUs BCPU1B and LCPU1L, respectively, to control each unit and control communication between the units. .

Next, the operation of the fourth embodiment will be described with reference to the flowcharts shown in FIGS. FIG. 12 shows the operation on the camera body unit side.
FIG. 11 shows the operation on the lens unit side, for example, assuming the driving of an autofocus lens.

First, when the amount of defocus is calculated by an unillustrated autofocus sensor, a lens driving mode starts (step S51). Next, BCPU
The number of driving pulses corresponding to the amount of defocus and the driving start command are transmitted from 1B to the LCPU 1L, and the LCPU 1L receives them (Steps S52 and S72). The communication at this time is serial communication, and the data output direction is determined by the BIO (see FIG. 10) of the camera body unit side output, and LDT (see FIG. 10) is a bidirectional data line.
LCLK (see FIG. 10) is a synchronous clock output from the LCPU 1L.

Next, D from BCPU1B to LCPU1L
The DC voltage detection data of the DC power supply 7 detected by the C voltage detection circuit 6 is transmitted (step S53, step S7).
3). With reference to the DC voltage detection data, the starting frequency f
s and pulse width Wn and L of switching pulse corresponding to voltage
The CPU 1L reads out the data from the memory in the lens unit LY (step S54) and transmits it to the BCPU 1B (steps S55 and S74).

Thereafter, the starting frequency fs and the pulse width W
Upon receiving the signal of n, the BCPU 1B sets the latches 31 and 41 of the oscillation circuit 3 and the pulse width setting circuit 4, and outputs the pulse signal φUSR (step S75). In response to the pulse signal φUSR, the LCPU 1L starts the pulse conversion circuit 5, outputs switching pulses of the pulse signals φ1 to φ4, and starts driving the motor (step S5).
6).

Thereafter, the monitor electrode 1 of the ultrasonic motor 10
Monitor signal VM from 0M and 1 from pulse conversion circuit 5
The phase of the output pulse signal φ1 is compared with that of the pulse signal φ1, and the phase difference is read from the phase difference counter 8 (step S5).
7) The LCPU 1L transmits a control command to the BCPU 1B so that the value becomes a predetermined value (step S5).
8, step S59, step S62, step S76
To step S81), changing the frequency to obtain the optimum frequency f
The ultrasonic motor 10 is driven by r.

The pulse signal from the rotary encoder 11 is counted by the LCPU 1L (step S60), and when the driving of the predetermined number of pulses is completed, a stop signal is transmitted to the BCPU 1B (step S61). When the BCPU 1B receives the stop signal (step S77), it exits the mode (steps S63 and S80).

According to the fourth embodiment, the camera body unit detects the voltage when the lens unit uses the DC power supply in the camera body unit.
The configuration of the lens unit is simplified. In this embodiment, since the oscillation circuit 3 and the pulse width setting circuit 4 are built in the camera body unit, a high-frequency oscillation circuit often used in the camera body unit can be used efficiently.

In the fourth embodiment, the oscillation circuit 3 and the pulse width setting circuit 4 are built in the body unit.
These may be provided in the lens unit 1L.

In this embodiment, an example in which the speed control is not performed has been described. However, in order to increase the stop accuracy of the ultrasonic motor, a constant residual pulse immediately before the stop operation is used in the second and third embodiments. It is also possible to use speed control such as deceleration control together in such a manner.

As described above, in the fourth embodiment, the built-in D
The photographing optical system can be driven without being affected by the power supply voltage of the C power supply and without generating an abnormal sound. Also,
Since the memory 2 is built in the lens unit, it is possible to store an optimum value in the adjustment process according to each of the lens unit and the ultrasonic motor.

As described above, according to each of the above-described embodiments, even if a DC power supply having a large voltage fluctuation is used, the ultrasonic motor can be driven at a frequency close to the resonance point without generating abnormal noise. And the required output is obtained. Further, since a DC-DC converter or the like for a motor power supply is unnecessary, the circuit scale can be reduced, and the cost can be reduced. Further, if the drive is performed near the resonance point, the efficiency of using the power of the power supply can be increased.

[0069]

As described above, according to the present invention, an abnormal noise is generated even when the power supply voltage fluctuates greatly.
Therefore, it is possible to provide a small and low-cost ultrasonic motor drive circuit capable of obtaining a sufficient mechanical output without causing such problems as the above.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram of an ultrasonic motor drive circuit showing a first embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing configurations of an oscillation circuit, a pulse width setting circuit, and a pulse conversion circuit in the ultrasonic motor drive circuit of the first embodiment.

FIG. 3 is an electric circuit diagram showing a phase difference counter and a waveform shaping circuit in the ultrasonic motor drive circuit of the first embodiment.

FIG. 4 is a timing chart showing signal waveforms at various parts of the ultrasonic motor drive circuit according to the first embodiment.

FIG. 5 is a flowchart showing the operation of the ultrasonic motor drive circuit of the first embodiment.

FIG. 6 is a diagram showing a pulse width at which an abnormal sound starts to be generated when the ultrasonic motor driving circuit of the first embodiment is driven at an optimum frequency for each voltage.

FIG. 7 is a flowchart showing the operation of the ultrasonic motor drive circuit according to the second embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between an optimum driving frequency and a rotation speed in the ultrasonic motor driving circuit according to the second embodiment.

FIG. 9 is a flowchart showing the operation of the ultrasonic motor drive circuit according to the third embodiment of the present invention.

FIG. 10 is an electric circuit diagram of an ultrasonic motor drive circuit showing a fourth embodiment of the present invention.

FIG. 11 is a flowchart showing an operation on the lens unit side in the ultrasonic motor drive circuit of the fourth embodiment.

FIG. 12 is a flowchart showing an operation on the camera body unit side in the ultrasonic motor drive circuit of the fourth embodiment.

[Explanation of symbols]

 Reference Signs List 1 CPU 2 Memory 3 Oscillation circuit 4 Pulse width setting circuit 5 Pulse conversion circuit 6 DC voltage detection circuit 7 DC power supply 8 Phase difference counter 9 Waveform shaping circuit 10 Ultrasonic motor 11 Rotary encoder

Claims (2)

(57) [Claims] An electric current flowing through a coil connected to a DC power supply
Is generated when switching
And generating an AC signal based on the induced electromotive force.
To the electro-mechanical energy conversion element of the ultrasonic motor
In the ultrasonic motor driving circuit for driving the ultrasonic motor, the voltage detecting means for detecting the voltage of the DC power supply and the pulse width of the switching pulse are set according to the voltage detected by the voltage detecting means. Pulse width setting means; monitoring means for detecting a driving state of the ultrasonic motor; and frequency control means for controlling a frequency of the AC signal based on an output of the monitoring means. Sound wave motor drive circuit. 2. A current flowing through a coil connected to a DC power supply.
Is generated when switching
And generating an AC signal based on the induced electromotive force.
To the electro-mechanical energy conversion element of the ultrasonic motor
An ultrasonic motor drive circuit that drives an ultrasonic motor by performing voltage detection means for detecting a voltage of the DC power supply, and a range of a pulse width of a switching pulse according to the voltage detected by the voltage detection means. Pulse width range setting to be set
Means and a monitoring means for detecting a driving state of the ultrasonic motor, the path of the pulse width based on the output of the monitor means
An ultrasonic motor drive circuit, comprising: pulse width control means for controlling a pulse width within a range of a pulse width.