JP2938628B2 - 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 for driving an ultrasonic motor.

[0002]

2. Description of the Related Art Conventionally, an ultrasonic motor using ultrasonic vibration as a driving force has been known. A traveling wave type ultrasonic motor, which is one type of ultrasonic motor, is configured as shown in FIG. 5 as an example. That is, the ultrasonic motor 80 includes an annular elastic body 82 made of a copper alloy or the like, and a piezoelectric body 84 (see also FIG. 6) is attached to the elastic body 82 to form a stator. The piezoelectric body 84 is a piezoelectric material that converts an electric signal into a mechanical vibration, and is configured by being divided and arranged in a ring shape by a large number of electrodes. On the other hand, the rotor 86 attached to the drive shaft 84 has a rotor ring 8 made of an aluminum alloy or the like.
An annular slider 90 is bonded to and formed on the elastic member 8, and the slider 90 is pressed against the elastic body 82 by a spring 92. As the slider 90, for example, an engineering plastic or the like is used in order to obtain a stable frictional force and a friction coefficient, so that the rotor 86 can be driven with high efficiency.

A drive circuit 94 as shown in FIG. 6 is connected to such an ultrasonic motor 80. That is, the drive circuit 94 includes an oscillator 96 including a voltage controlled oscillator (hereinafter, referred to as a VCO). The signal of the predetermined frequency output from the oscillator 96 is branched into two, one of which is amplified by the amplifier 98 and input to the piezoelectric body 84 as a sine wave drive signal, and the other is input to the phase shifter 100 to change the phase to 90. °, the signal is amplified by the amplifier 102 and cos
The signal is input to the piezoelectric body 84 as a wave drive signal. As a result, a standing wave of ultrasonic vibration caused by a driving signal of a sine wave and a standing wave of ultrasonic vibration having a different phase from the vibration are excited by a driving signal of a cosine wave in the piezoelectric body 84, and the elastic body 82. When these two standing waves are superimposed, an ultrasonic vibration, that is, a so-called traveling wave, in which antinodes and nodes of the vibration move in an annular shape along the elastic body 82, is generated. The traveling wave is transmitted as a rotational force in a direction opposite to the traveling direction of the traveling wave to the rotor 86 pressed against the elastic body 82, and the rotor 86 and the drive shaft 84 rotate.

As described above, the ultrasonic motor has a simple structure that does not require a coil or a magnet as compared with a conventional motor, so that it is excellent in mass productivity and small in size and light in weight and has a high responsiveness, so that it is versatile. High and high torque during low-speed rotation makes it unnecessary to use a gear or the like to reduce rotation.
For this reason, these ultrasonic motors have recently been widely used for lens driving of cameras, automobile electric components, office automation equipment and the like.

The ultrasonic motor is controlled by controlling the oscillation frequency of the oscillator of the drive circuit. For example, the impedance of the ultrasonic motor changes as shown in FIG. 3 according to the change in the frequency of the drive signal applied to the ultrasonic motor, and the rotational speed and torque of the rotor change according to the change in the impedance. When a drive signal having a frequency corresponding to the resonance region of the impedance in the characteristic diagram shown in FIG. 3 is supplied to the ultrasonic motor, the output of the ultrasonic motor is small, and an audible sound may be generated. For this reason, when the driving of the ultrasonic motor is started, the frequency of the driving signal is gradually changed from a high band to a low band so that the driving is performed while avoiding the resonance region.

[0006]

However, in the conventional ultrasonic motor drive circuit, since the oscillator is constituted by the VCO, the control voltage applied to the VCO corresponds to the frequency of the drive signal supplied to the ultrasonic motor. Therefore, it was necessary to adjust the variable resistor of the VCO at the time of shipment. Since the adjustment of the variable resistor is performed manually, the productivity is not good. Further, since the variable resistor cannot be incorporated in an integrated circuit such as an LSI, the drive circuit of the ultrasonic motor cannot be downsized.

To solve this problem, a crystal oscillator is oscillated to obtain a high-frequency high-speed clock, the number of pulses of the high-speed clock is counted, and a pulse is output when a predetermined count value is reached. A digital driving circuit that generates an ultrasonic motor driving frequency signal obtained by dividing a clock is considered. Since this drive circuit does not use a variable resistor, the adjustment at the time of shipment as described above is unnecessary, and the drive circuit can be incorporated in an integrated circuit. But,
In such a driving circuit, the minimum step width when changing the frequency is large.

[0008] As shown in FIG. 7 as an example, when dividing the frequency of the high-speed clock count value D by dividing the 10 MHz _Z as 250, the frequency _{f = 10MH Z ÷ 250 = 40KH} Z
Drive signal can be obtained, but when the count value D ₊₁ = 251 adds "1" to the count value, the frequency of the drive signal changes to the frequency _{f-α = 10MH Z ÷ 251} = 39.841MH Z. Therefore, the step width of the frequency change of the drive signal is about 16
Is 0 H _Z. The same applies when “1” is subtracted from the count value. When the frequency is digitally changed, the vibration generated in the motor body due to the rapid change in the amplitude of the traveling wave is suppressed, and the ultrasonic motor is driven without generating an audible sound. 10H are the in step width is required to change the frequency of the drive signal of the _Z, there is a problem that it is impossible to smoothly drive the ultrasonic motor.

[0009] to reduce the step size of a change in the frequency of the drive signal in the drive circuit, but in order to smoothly drive the ultrasonic motor, it is necessary to the frequency of the high-speed clock of about 200 MH _Z, at this rate Creating a synchronous oscillator is very difficult with current technology. When the frequency of the high-speed clock is increased, the number of digits of the count value increases, the number of bits of the digital circuit increases, and the circuit becomes large-scale.

In the digital drive circuit, a high-speed clock may be generated by a VCO to change the frequency of the high-speed clock.
The above-mentioned problems of the VCO cannot be solved.

The present invention has been made in view of the above facts, and has as its object to provide an ultrasonic motor drive circuit capable of improving productivity and driving the ultrasonic motor smoothly. It is.

[0012]

In order to achieve the above object, a driving circuit for an ultrasonic motor according to the present invention comprises: an oscillator;
A variable capacitance diode whose capacitance is determined according to the supplied voltage, an oscillation circuit that outputs a signal having a resonance frequency according to the supplied voltage, and converts input digital data to an analog voltage. Supply means for supplying the analog voltage to the variable capacitance diode; and a signal output from the oscillation circuit, which is frequency-divided at a set frequency division ratio, and outputs the frequency-divided signal as a signal for driving an ultrasonic motor. A signal output unit; and a setting unit that inputs the digital data to the supply unit and sets the frequency division ratio in the drive signal output unit.

Preferably, the oscillator is a ceramic oscillator.

[0014]

According to the present invention, an oscillating circuit is configured to output a signal having a resonance frequency of an oscillator according to the supplied voltage by using a variable capacitance diode whose capacitance is determined according to the supplied voltage. ing. Therefore, by gradually changing the value of the digital data input to the supply means and finely adjusting the voltage supplied to the variable capacitance diode, the frequency of the signal output from the oscillation circuit can be finely adjusted. In the present invention, since the drive signal of the ultrasonic motor is obtained by dividing the signal output from the oscillation circuit by the division ratio set in the signal output means, the value of the digital data set in the supply means by the setting means By changing the frequency division ratio set in the signal output means, the frequency of the drive signal can be changed over a wide range with a small step width.

As described above, according to the present invention, the frequency of the drive signal can be changed by changing the value of the digital data and the frequency division ratio, and the variable capacitance diode has a mechanically movable part unlike a variable resistor. Since there is no need to adjust the variable resistor at the time of shipment, productivity can be improved. In addition, since the frequency of the drive signal can be changed over a wide range with a small step width as described above, various types of ultrasonic motors can be driven smoothly.

In the present invention, the oscillator is preferably a ceramic oscillator. A ceramic oscillator has a wider range of change in the resonance frequency due to a change in the time constant of the oscillation circuit than a crystal oscillator, and the resonance frequency greatly changes with a change in the capacitance of the variable capacitance diode. For this reason,
The frequency of the signal output from the oscillation circuit can be easily changed, and the configuration of the oscillation circuit can be simplified.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a schematic configuration of an ultrasonic motor drive circuit 10 according to the present invention, and FIG. 2 schematically shows an ultrasonic motor oscillation circuit 14 which forms a part of the ultrasonic motor drive circuit 10. The configuration is shown.

The ultrasonic motor oscillation circuit 14 includes a ceramic oscillator 16. One end of the ceramic oscillator 16 has one end of a capacitor 18 and the other end has a capacitor 20.
Are connected to each other, and the other end of the capacitor 18 is grounded. The other end of the capacitor 20 is connected to the cathode of the variable capacitance diode 22. The anode of the variable capacitance diode 22 is grounded. The variable capacitance diode 22 has a capacitance C (junction capacitance of a PN junction) determined according to the magnitude of a voltage applied to both ends, and is widely used in a tuning circuit and the like. A resistor 24 and an inverter 26 are connected in parallel to the ceramic oscillator 16.

The ceramic oscillator 16, the inverter 26, the resistor 24, the capacitors 18, 20 and the variable capacitance diode 22 constitute an oscillation circuit 28 for oscillating the ceramic oscillator 16. The inverter 26 is connected to a power supply (not shown), and the oscillation circuit 28 causes the ceramic oscillator 16 to oscillate by the power supplied via the inverter 26. The resonance frequency of the ceramic oscillator 16 is determined according to a time constant based on the combined capacitance of the capacitor 20 and the variable capacitance diode 22 of the oscillation circuit 28, the capacitance of the capacitor 18, and the resistance value of the resistor 24. It has become.

With the ceramic oscillator 16 oscillating,
The variable capacitance diode 22 (the V ₁₎ constant voltage is applied, the capacitance C of the variable capacitance diode 22 becomes a value corresponding to a constant voltage V _1. In the oscillation circuit 28 becomes a predetermined time constant when constant voltages V ₁ across the variable capacitance diode 22 is applied, so that the signal 12MH _Z is obtained ceramic resonator 16 vibrates at the resonant frequency 12MH _Z In addition, the capacitances of the capacitors 18 and 20 and the resistance value of the resistor 24 are defined. The output terminal of the inverter 26 is connected to the input terminals of the counters 30 and 32, and the signal of the resonance frequency output from the ultrasonic motor oscillation circuit 28 is input to the counters 30 and 32 as a high-speed clock.

On the other hand, one end of a resistor 34 is connected between the capacitor 20 and the variable capacitance diode 22, and the other end of the resistor 34 is connected to a D / A converter (digital / analog converter) 36. I have. Oscillation circuit for ultrasonic motor 1
4 is connected to a frequency determination circuit 62 described later via 16 buses 38, so that 16-bit data is supplied. The D / A converter 36 has the 16
Six of the buses 38 are connected to the input terminal, and the frequency determination circuits 62 to
Bit digital data is input, and the digital data is converted into analog data (analog voltage) and converted to a resistor 34.
Supply to

Therefore, the variable capacitance diode 22 has D
A voltage (referred to as V ₂ ) corresponding to the value of digital data input via the bus 40 is applied to the / A converter 36.
The voltage V ₂ is such that the value of the 6-bit digital data is (000
000) In the case of ₂ , the voltage is 0 V, and is increased as the value of the digital data increases. Therefore, a voltage of V ₁ + V ₂ is applied to both ends of the variable capacitance diode 22 while the ceramic oscillator 16 is oscillating.
In the variable capacitance diode 22, the capacitance C decreases as the applied voltage increases, and accordingly, the time constant of the ultrasonic motor oscillation circuit 28 is changed, and the frequency (resonance frequency) of the signal output as the high-speed clock is changed. ) Will be raised gradually.

In this embodiment, the value of the digital data is (00000
When set to 1) _2, the resistance value or the like of the resistor 34 so that the frequency of the signal is 12.001MH _Z is set. When the value of the digital data input to D / A converter 36 (000000) from ₂ to (111111) ₂ is changed as described above, the signal output from the oscillation circuit 28, i.e. the frequency of the high-speed clock 12MH _Z From the above, it changes with the same step width as described above.

On the other hand, the ten buses 42 not connected to the D / A converter 36 in the 16 buses 38 are branched into two, and each of the branched buses is an input of the counter 30 or the counter 32. Connected to the end. Counter 30,
32 is supplied with 10-bit data as a frequency division ratio from a frequency determination circuit 62 via a bus 42. The output terminal of the counter 30 is the S terminal of the set / reset latch 44.
The output terminal of the counter 32 is connected to the R (reset) terminal of the set / reset latch 44. Counters 30, 32 and latch 44
Divides the inputted high-speed clock by the inputted dividing ratio.

That is, the counters 30 and 32 count the pulses of the high-speed clock input from the oscillation circuit 28 in accordance with the input division ratio, and output a pulse to the latch 44 every time the counting is completed. Counter 30,
The pulse output from the terminal 32 is connected to the S terminal of the latch 44 and the R terminal.
The signal is input to the terminal, whereby one pulse is output from the latch 44. By continuing the above operation, if the set dividing ratio is 1 / n, the latch 44 outputs a signal having a cycle of n times the cycle of the high-speed clock.

As shown in FIG. 1, the output terminal of the ultrasonic motor oscillation circuit 14 is branched into two, one of which is connected to the input terminal of the amplifier circuit 46. The output terminal of the amplifier circuit 46 is connected to an electrode of a piezoelectric body 54 of the ultrasonic motor 12 which will be described later, amplifies the input signal, and supplies the signal to the ultrasonic motor 12 as a sine wave drive signal. The other side is connected to an input terminal of an amplifier circuit 48 via a phase shifter 50. The output terminal of the amplifier circuit 48 is connected to the electrode of the piezoelectric body 54 of the ultrasonic motor 12 in the same manner as described above. The phase shifter 50 shifts the phase of the input signal by 90 °. The signal shifted in phase by the phase shifter 50 is amplified by the amplifier circuit 48 and supplied to the ultrasonic motor 12 as a cos wave drive signal. You.

The ultrasonic motor 12 has an annular elastic body 52 made of a copper alloy or the like, and the above-mentioned piezoelectric body 54 is attached to the elastic body 52 to form a stator 56. The piezoelectric body 54 is a piezoelectric material that converts an electric signal into a mechanical vibration, and is configured by being divided and arranged in an annular shape by a number of electrodes. On the other hand, a rotor 58 attached to a drive shaft (not shown) is formed by bonding an annular slider to a rotor ring made of an aluminum alloy or the like, and the slider of the rotor 58 is applied to the elastic body 52 by a spring (not shown). Pressure contact. As this slider,
In order to obtain stable frictional force and friction coefficient, for example, engineering plastics and the like are used.

The piezoelectric body 54 of the ultrasonic motor 12 is connected to a frequency tracking circuit 60. Frequency tracking circuit 6
0 detects the driving state of the piezoelectric body 54. An output terminal of the frequency tracking circuit 60 is a frequency determination circuit 62
It is connected to the. The frequency determination circuit 62 determines the frequency of the D / A converter 3 based on the frequency detected by the frequency tracking circuit 60.
6 and the values of digital data and counters 30 and 3
The frequency division ratio set to 2 is determined and supplied to the ultrasonic motor oscillation circuit 14 via the 16 buses 38.

Next, the operation of this embodiment will be described. When the driving of the ultrasonic motor 12 is started, first, a driving signal of a predetermined frequency on a high frequency side in the impedance characteristic of the ultrasonic motor shown in FIG. 3 is supplied to the ultrasonic motor, and then the frequency of the driving signal is gradually lowered. I am trying to do it. For this reason, the frequency determination circuit 62 determines that the frequency of the drive signal is, for example, f
Determine the division ratio and the value of the digital data so that
The division ratio and the digital data are set via the bus 38. As a result, the sine wave and the cosine wave having the frequency f are supplied to the ultrasonic motor 12 as drive signals, and the standing waves of the ultrasonic vibration corresponding to the sine wave and the cosine wave are superimposed to generate a traveling wave. This traveling wave is transmitted to the rotor 58 as a rotational force, and the rotor 58 is rotated to start driving the ultrasonic motor 12.

Next, the frequency determination circuit 62 gradually lowers the frequency of the drive signal. For example, the frequency at the start of driving is 40K
In the case of H _Z is the initial value of the digital data (000000) ₂
If 1/300 was division ratio 1 / D and the resonant frequency of the ceramic resonator 16 is 12MH _Z, and the ultrasonic motor 12
Driving signal of a frequency _{f = 12MH Z / 300 = 40KH} Z is supplied to the. When the frequency of the drive signal is lowered from this state, the value of the digital data is (000000) ₂ , so the frequency determination circuit 62 adds “1” to the D (D _{+1 in} FIG. 4) and frequency of the drive signal to a predetermined value the value of the digital data so as to change by a predetermined step width (e.g., about 3H _Z).

When the frequency is to be further reduced, the process of subtracting "1" from the value of the digital data at predetermined time intervals is repeated while D _{+ 1} is kept constant, so that the frequency of the drive signal is gradually and stepwise. To lower. Accordingly, the impedance of the ultrasonic motor 12 changes, and the rotational speeds of the rotor 58 and the drive shaft gradually change toward the target rotational speed. The step width of the change in the frequency of the drive signal when the ultrasonic motor oscillation circuit 14 of this embodiment the digital data is varied one by "1" is set to about 3H _Z, frequency for driving the ultrasonic motor 12 Is sufficiently small as the step width of the change. Therefore, no vibration or audible sound is generated in the ultrasonic motor 12. By repeating the process of subtracting “1” from the value of the digital data, the frequency of the drive signal is changed from f to f−α as shown in FIG.
, And gradually lower gradually. When the value of the digital data becomes (000000) ₂ , the frequency of the drive signal becomes f-α in FIG. Note frequency of the drive signal at this time is, in the above example _{f-α = 12MH Z / 301} = 39.867
KH _Z.

When a load is applied to the ultrasonic motor 12, the impedance characteristic of the ultrasonic motor 12 changes as shown by the imaginary line in FIG. When the temperature of the ultrasonic motor 12 rises, the impedance characteristic of the ultrasonic motor 12 changes as shown by a broken line in FIG. In this case, the rotational speed of the ultrasonic motor 12 changes with the change in the impedance of the ultrasonic motor 12. Therefore, the frequency determination circuit 62 changes the frequency of the drive signal so that the rotational speed of the ultrasonic motor 12 becomes constant.

[0033] The ultrasonic motor 1
The frequency of the drive signal to be supplied to 2 is, for example, frequency f = 40K
If the gradually increasing from H _Z, the frequency determining circuit 62
Repeats the process of adding "1" to the value of the digital data every predetermined time without changing the set dividing ratio, and setting the value to the D / A converter 36 via the bus 40. Frequency f = 40KH division ratio 1 / D initial value of the digital data in the (000000) ₂ as described above in the case of _Z is 1/300. Adds "1" to the value of the digital data, setting (000001) ₂ to the D / A converter 36, the frequency of the drive signal output from the oscillation circuit 28 becomes 12.001MH _Z, the frequency of the drive signal the 12.001MH _Z / 300 = 40.003K
The H _Z.

[0034] As described above, the step width of the change in frequency at this time is also 3H _Z, since sufficiently small as step size of a change in frequency for driving the ultrasonic motor 12 vibrates in the ultrasonic motor 12 No audible sound is generated. By repeating the process of adding “1” to the value of the digital data, the frequency of the drive signal is gradually and gradually increased from f to f + α as shown in FIG.

After the frequency of the drive signal becomes a frequency close to f + α in FIG. 4 and the value of the digital data becomes a predetermined value, the value of the digital data is set to (000000) ₂ and the value of “1” is changed from D. Subtraction is performed (D _{-1 in} FIG. 4). This allows
Frequency of the drive signal becomes f + alpha, for example, as a frequency _{f + α = 12MH Z / 299} = 40.133KH Z in the above. Also in this case, the frequency of the drive signal is brought close to f + α by changing the value of the digital data as described above, so that the frequency of the drive signal does not greatly change, and No audible sound is generated.

As described above, in the present embodiment, the oscillation circuit 28 is configured to change the resonance frequency of the ceramic oscillator 16 by changing the voltage applied to both ends of the variable capacitance diode. The step width of the change can be reduced, and the ultrasonic motor 12
Can be driven smoothly.

Further, in this embodiment, since the frequency of the drive signal can be changed without using a variable resistor, it is not necessary to adjust the variable resistor at the time of shipment, and the VC
The productivity of the ultrasonic motor oscillation circuit 14 can be improved as compared with the oscillation circuit using O.

In this embodiment, the analog voltage is handled by the D / A converter 36. However, in the current ASIC (application-specific IC) technology, not only digital circuits but also digital circuits are used.
Some analog components such as the / A converter can be housed in a one-chip integrated circuit. Therefore, the counters 30 and 32 and the latch 4 in the ultrasonic motor oscillation circuit 14 of FIG.
4, the frequency tracking circuit 60 and the frequency determination circuit 6 in the D / A converter 36 and the driving circuit 10 of the ultrasonic motor in FIG.
2 and the phase shifter 50 can be housed in a one-chip integrated circuit. For this reason, the drive circuit 10 of the ultrasonic motor can be reduced in size as compared with the related art.

The oscillation circuit 28 may be configured as shown in FIG. In FIG. 8, a variable capacitor 22 is connected in series with the capacitor 18, and one end of the capacitor 20 is grounded. The variable capacitor 22 has D
A voltage is supplied from the / A converter 36. In this case, the resonance frequency of the ceramic oscillator 16 depends on the combined capacitance of the capacitor 18 and the variable capacitance diode 22 and the capacitance of the capacitor 20.
And the time constant based on the capacitance of the resistor 24 and the resistance value of the resistor 24.

The oscillation circuit 28 may be configured as shown in FIG. In FIG. 9, a variable capacitance diode 22B is connected in series with the capacitor 18, and a variable capacitance diode 22A is connected in series with the capacitor 20. D / A
The voltage from the converter 36 is supplied to the variable capacitance diodes 22A and 22B. The ceramic oscillator 16 in this case
Is determined according to a time constant based on the combined capacitance of the capacitor 18 and the variable capacitance diode 22B, the combined capacitance of the capacitor 20 and the variable capacitance diode 22A, and the resistance value of the resistor 24. In the oscillation circuit shown in FIG.
Since the capacitance of the variable capacitance diodes 22A and 22B changes according to the voltage from the / A converter 36, the shift amount of the resonance frequency of the ceramic oscillator 16 increases.

In this embodiment, a ceramic oscillator is used as an oscillator. However, the present invention is not limited to this, and a crystal oscillator can be used as long as the shift amount of the resonance frequency is large.

[0042]

As described above, according to the present invention, a variable capacitance diode whose capacitance is determined according to a supplied voltage is used to output a signal having a resonance frequency of an oscillator according to the supplied voltage. The oscillation circuit is configured as described above, and the oscillation circuit for the ultrasonic motor that does not use the adjusting element is made. Therefore, the excellent effect that the productivity can be improved and the ultrasonic motor can be smoothly driven can be obtained. can get.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a drive circuit of an ultrasonic motor according to an embodiment.

FIG. 2 is a schematic configuration diagram of an oscillation circuit for an ultrasonic motor that forms a part of a drive circuit of the ultrasonic motor.

FIG. 3 is a diagram illustrating a change in impedance of an ultrasonic motor when a frequency of a drive signal is changed.

FIG. 4 is a diagram showing a step width of a change in frequency of a drive signal output from the ultrasonic motor oscillation circuit of the present embodiment.

FIG. 5 is a perspective view showing a schematic configuration of an ultrasonic motor.

FIG. 6 is a schematic configuration diagram of a drive circuit of a general ultrasonic motor.

FIG. 7 is a diagram showing a step width of a change in frequency of a drive signal output from a digital oscillation circuit.

FIG. 8 is a schematic configuration diagram showing another example of the oscillation circuit for the ultrasonic motor.

FIG. 9 is a schematic configuration diagram showing another example of the oscillation circuit for the ultrasonic motor.

[Explanation of symbols]

 10 Ultrasonic Motor Drive Circuit 12 Ultrasonic Motor 14 Ultrasonic Motor Oscillation Circuit 16 Ceramic Oscillator 22 Variable Capacitance Diode 30 Counter 32 Counter 36 D / A Changer 44 Latch 62 Frequency Determination Circuit

Claims (2)

(57) [Claims] 1. An oscillation circuit comprising: an oscillator; and a variable capacitance diode whose capacitance is determined according to a supplied voltage, and an oscillation circuit that outputs a signal having a resonance frequency according to the supplied voltage. Supply means for converting the digital data into an analog voltage and supplying the analog voltage to the variable capacitance diode; and dividing the signal output from the oscillation circuit by a set frequency division ratio to exceed the frequency-divided signal. An ultrasonic motor drive circuit, comprising: signal output means for outputting a signal for driving an ultrasonic motor; and setting means for inputting the digital data to the supply means and setting the frequency division ratio in the drive signal output means. . 2. The ultrasonic motor drive circuit according to claim 1, wherein said oscillator is a ceramic oscillator.