JP4765405B2 - Ultrasonic motor drive device - Google Patents

Description

  The present invention relates to an ultrasonic motor driving apparatus.

  AC that has a piezoelectric element (electromechanical transducer) attached to one plane of an elastic body formed in a ring shape with metal or the like as a vibrator, and has a certain phase difference in the piezoelectric element A so-called ultrasonic motor is known which is a vibration wave actuator configured to excite a traveling wave on the other plane of an elastic body by applying an electric field (see Patent Document 1).

  The relationship between the mechanical resonance frequency fr of the vibrator in the ultrasonic motor, the drive frequency f1 that is the maximum number of rotations at which the ultrasonic motor rotates stably, and the drive frequency f0 at which the ultrasonic motor starts rotating is generally: fr <f1 <f0. On the other hand, in an ultrasonic motor drive circuit using a transformer, the resonance frequency fc due to the inductance L of the secondary winding of the transformer and the capacitance C of the vibrator of the ultrasonic motor is 1 / {2π√ (LC)}. However, it is desirable to match L and C so that fc = f0.

Japanese Patent Laid-Open No. 9-271174

  However, the frequency band between f0 and f1 may be wide depending on the characteristics of the ultrasonic motor. When fc = f0, if the drive frequency is lowered from f0, free vibration occurs between the transducer and the vibrator of the ultrasonic motor, the drive voltage waveform of the ultrasonic motor is disturbed, and the input power increases. Occurs. Furthermore, depending on the characteristics of the ultrasonic motor, even if a driving voltage of a certain level or more is applied, it becomes heat energy and the efficiency may decrease.

  The present invention provides an ultrasonic motor driving device that reduces power loss of a circuit and supplies optimal power to the ultrasonic motor.

The invention according to claim 1 is an ultrasonic motor driving device that drives an ultrasonic motor having a vibrator and a relative motion member that is pressed against the vibrator and driven by the vibration of the vibrator. A transformer for connecting a DC power source to the side winding and supplying a voltage from the secondary winding to the vibrator; first switching means for turning on and off a current flowing through the primary winding of the transformer; and the transformer Second switching means for turning on and off the current flowing in the secondary side winding, third switching means for turning on and off the current flowing in the primary side winding of the transformer, the first switching means and the second controlling on and off of the switching means and the third switching means, and, while turning on the first switching means, said third predetermined period of time off the switching means Characterized in that it comprises a switching control means for cormorants control.
The invention according to claim 9 is an ultrasonic motor driving device that drives an ultrasonic motor having a vibrator and a relative motion member that is pressed against the vibrator and driven by the vibration of the vibrator. A transformer for connecting a DC power source to the side winding and supplying a voltage from the secondary winding to the vibrator; first switching means for turning on and off a current flowing through the primary winding of the transformer; and the transformer Second switching means for turning on and off the current flowing through the primary winding, and switching control means for controlling on / off of the first switching means and the second switching means, the switching control means comprising: The first switching means is controlled to drive the ultrasonic motor by turning on and off at a predetermined cycle, and the first switching means is operated within the predetermined cycle. The stage after the first predetermined time period off, when said first switching means is a second predetermined period on, the second short third predetermined time period than the switching means and the second predetermined time period It is characterized by controlling to turn off.

  Since the present invention is configured as described above, the free vibration generated on the secondary side of the transformer can be suppressed, and as a result, power loss can be reduced and optimum power is supplied to the ultrasonic motor. be able to. Furthermore, malfunctions caused by free vibration can be prevented.

-First embodiment-
FIG. 1 is a diagram showing a configuration of an ultrasonic motor driving apparatus according to a first embodiment of the present invention. The ultrasonic motor 1 according to the present embodiment is a rotary ultrasonic motor, and includes an annular vibrator and an annular relative motion member (also referred to as a rotor or a mover). An annular vibrator is composed of an annular elastic body and an annular piezoelectric element (electromechanical energy conversion element) bonded to the elastic body. The annular piezoelectric element has electrodes appropriately polarized in the circumferential direction. (For example, about 12 poles).

  Two alternating current signals whose phases are shifted by 90 degrees are combined with their inverted signals and supplied alternately to the polarized electrodes as appropriate for each polarized electrode. As a result, the piezoelectric element is vibrated to generate a traveling wave vibration in the elastic body. The relative motion member in pressure contact with the elastic body is driven to rotate by receiving the vibration of the traveling wave generated in the elastic body.

  In FIG. 1, in order to simplify the drawing, two AC signals whose phases are shifted by 90 degrees are described as being supplied to the two piezoelectric elements 1a and 1b. However, the piezoelectric element 1a means all polarized piezoelectric elements to which one AC signal and its inverted signal are supplied, and the piezoelectric element 1b is a polarized piezoelectric element to which the other AC signal and its inverted signal are supplied. It shall mean all elements.

  In FIG. 1, the ultrasonic motor driving device includes a DC power supply circuit 2, a pulse generation circuit 3, switching control circuits 4 and 5, and driving circuits 6 and 7. The drive circuit 6 includes a transformer 11, MOSFETs 12 and 13, diodes 14 and 15, and an inverter 16. Similarly to the drive circuit 6, the drive circuit 7 includes a transformer 21, MOSFETs 22 and 23, diodes 24 and 25, and an inverter 26.

  FIG. 2 is a diagram illustrating an internal configuration of the switching control circuit 4. As shown in FIG. 2, the switching control circuit 4 includes a resistor 31, a diode 32, a Schmitt trigger buffer 33, a resistor 34, a capacitor 35, a Schmitt trigger inverter 36, an inverter 37, a flip-flop 38, and a NAND gate 39. The operation of the switching control circuit 4 will be described later. The switching control circuit 5 has the same configuration as the switching control circuit 4.

  FIG. 3 is a diagram showing the drive frequency versus rotational speed (rotational speed) characteristics of the ultrasonic motor 1. f0 is a drive frequency at which the ultrasonic motor 1 starts rotating, f1 is a drive frequency at which the maximum rotation speed of the control range is reached, and fr is a drive frequency at which mechanical resonance occurs in the vibrator of the ultrasonic motor 1. . In the present embodiment, in consideration of control stability and the like, a characteristic that is lower than the drive frequency fr corresponding to the mechanical resonance of the vibrator of the ultrasonic motor 1 is used. That is, control is performed to increase the rotational speed of the ultrasonic motor 1 by lowering the drive frequency from the drive frequency f0.

  In the ultrasonic motor driving apparatus configured as described above, the pulse generation circuit 3 has a phase of the driving frequency f corresponding to the desired rotational speed N of 90 degrees in order to rotate the ultrasonic motor 1 at the desired rotational speed N. Two shifted pulse signals P1 and P2 are output. The pulse signals P1 and P2 output from the pulse generation circuit 3 become the signals B1 and B2 through the switching control circuits 4 and 5 to turn on and off the MOSFETs 12 and 22 of the drive circuits 6 and 7, respectively. By turning on and off the MOSFETs 12 and 22, boosted signals C 1 and C 2 having the same frequency f as the pulse signal are generated on the secondary winding side of the transformers 11 and 21.

  The boosted signals C1 and C2 generated on the secondary winding side are supplied to the piezoelectric elements 1a and 1b, and the piezoelectric elements 1a and 1b vibrate at the same frequency f as the pulse signal. The signals C1 and C2 are 90 degrees out of phase. As described above, the piezoelectric element 1a is a set of a plurality of polarized piezoelectric elements, and is a set of piezoelectric elements to which the signal C1 and the signal -C1 are supplied. Similarly, the piezoelectric element 1b is a set of a plurality of polarized piezoelectric elements, and is a set of piezoelectric elements to which the signal C2 and the signal -C2 are supplied. The signal -C1 and the signal -C2 are signals that are wired with the ground and each signal wiring reversed with respect to the signals C1 and C2. When the signals C1 and C2 are thus supplied to the piezoelectric elements 1a and 1b, traveling waves are generated in the elastic bodies joined to the piezoelectric elements 1a and 1b. The relative motion member in pressure contact with the elastic body receives vibrations of traveling waves generated in the elastic body and is rotationally driven at a rotational speed N corresponding to the drive frequency f.

  In the present embodiment, when the ultrasonic motor 1 is driven in this way, it is provided on the series circuit of the secondary windings of the transformers 11 and 21 and the piezoelectric elements 1a and 1b in the cycle of the driving frequency f. By turning off the MOSFETs 13 and 23 for a certain period, free vibrations generated between the transformers 11 and 21 and the piezoelectric elements 1a and 1b are suppressed. Hereinafter, this control will be described in more detail.

  FIG. 4 is a timing chart for driving the ultrasonic motor 1. The operation for suppressing free vibration in the drive circuit 6 and the drive circuit 7 is based on the same principle. Therefore, as an example, the operation in the drive circuit 6, that is, the supply of a signal to the piezoelectric element 1a will be described.

  As shown in FIG. 4A, the pulse generation circuit 3 outputs a pulse signal P1 having a desired frequency (period t1-t4). The switching control circuit 4 inputs the pulse signal P1 and the drive waveform feedback signal from the primary side of the transformer 11 of the drive circuit 6, and outputs a signal B1 shown in FIG. The generation of the signal B1 will be described later. The time t1-t2 of the signal B1 is a value determined by circuit constants such as the transformer 11 of the drive circuit 6, and cannot be controlled from the outside. That is, the value depends on the inductance L of the secondary winding of the transformer 11 and the resonance frequency fc of the electrostatic capacitance C of the piezoelectric element 1a, and does not depend on the drive frequency f. On the other hand, the time t1 to t4 of the signal B1 is a time determined by the drive frequency and is a value that can be controlled from the outside. Accordingly, when the time t1 to t4 becomes longer, the time t1 to t2 becomes constant, and therefore the time t2 to t4 becomes longer.

  As shown in FIG. 1, the signal B1 is input to the gate terminal of the MOSFET 12, the MOSFET 12 is turned off while the signal B1 is low (t1-t2), and the signal B1 is high (t2-t4). The MOSFET 12 is controlled to be turned on. On the other hand, the signal B1 is inverted by the inverter 16 and input to the gate terminal of the MOSFET 13, the MOSFET 13 is turned on while the signal B1 is low (t1-t2), and the MOSFET 13 is turned off while the signal B1 is high (t2-t4). The switching is controlled as follows.

  While the MOSFET 12 is on, the current I1 flows from the DC power supply circuit 2 to the primary winding of the transformer 11 (FIG. 4C), and energy is stored in the primary winding of the transformer 11. In this way, the MOSFET 12 is controlled to be turned on / off, whereby a driving voltage as shown in FIG. 4D is supplied to the piezoelectric element 1a.

  The driving voltage supplied to the piezoelectric element 1a is considered to generate free vibration after timing t2. However, in the present embodiment, this free vibration is suppressed by turning off the MOSFET 13 after the timing t2. That is, the occurrence of free vibration is suppressed by inserting the switching element of the MOSFET 13 on the series circuit between the piezoelectric element 1a, the secondary winding of the transformer 11 and the ground, and turning off the MOSFET 12.

  The relationship between the drive frequency and the drive voltage applied to the piezoelectric element 1a will be described. As shown in FIG. 4, since the MOSFET 12 is on from t2 to t4, the current I1 continues to flow during that time, the energy stored in the transformer 11 increases, and the voltage applied to the piezoelectric element 1a also increases. When the drive frequency is changed, the time from t2 to t4 changes as described above, so that the time from t2 to t4 becomes longer as the drive frequency is lowered. As a result, the voltage applied to the piezoelectric element 1a increases, the amplitude of the piezoelectric element 1a increases, and the rotational speed of the ultrasonic motor 1 increases.

  FIG. 5 is a timing chart illustrating a process in which the signal B1 is generated in the switching control circuit 4 of FIG. FIG. 5A shows a drive waveform feedback signal from the drive circuit 6, and shows a signal waveform at a terminal opposite to the terminal connected to the DC power supply circuit 2 of the primary winding of the transformer 11. . The waveform of the drive waveform feedback signal is shaped as shown in FIG. 5B through the resistor 31 and the diode 32, and further, a pulse signal as shown in FIG. 5C is outputted via the Schmitt trigger buffer 33. .

  The pulse signal shown in FIG. 5C has a waveform as shown in FIG. 5D through an integrating circuit of a resistor 34 and a capacitor 35, and the Schmitt trigger inverter 36 outputs a pulse signal having the timing shown in FIG. 5E. Is done. The constants of the resistor 34 and the capacitor 35 are determined so that the rise of the output of the Schmitt trigger inverter 36 comes at the timing t2, that is, around the lower limit point of the drive waveform feedback signal in FIG.

  The output of the Schmitt trigger inverter 36 is input to the clock terminal (CLK) of the flip-flop 38. At this time, the D terminal of the flip-flop 38 is always at ground. On the other hand, the pulse signal P1 (FIG. 5 (f)) from the pulse generation circuit 3 is inverted by the inverter 37 and input to the preset terminal (PRE) of the flip-flop 38.

  The flip-flop 38 to which such a signal is input outputs an inverted Q signal shown in FIG. 5G and outputs it as a signal A1. The signal A1 is a signal that is not used in the present embodiment, but is a signal that is used in the second embodiment. On the other hand, the non-inverted signal Q is NANDed by the output of the inverter 37 and the NAND gate 39, and the NAND gate 39 outputs the signal B1.

  Note that the ultrasonic motor driving apparatus of the present embodiment turns on the MOSFET 12 to store energy on the primary side of the transformer 11 and turns off the MOSFET 12 to generate a vibration signal (attenuation signal) generated on the secondary side of the transformer 11. ), Only the first waveform is used for driving the piezoelectric element 1a, and the subsequent waveforms are excluded as free vibration. It can be said that the switching control circuit 4 extracts the first waveform as an effective signal. The first waveform is a signal of the first half cycle of the vibration signal, and signals after the first half cycle are free vibration signals.

  The operation of the drive circuit 7 side and the switching control circuit 5 can also be described in the same manner using the timing charts of FIGS.

The ultrasonic motor driving device according to the first embodiment configured as described above has the following effects.
(1) The pulse output B1 that turns on the MOSFETs 12 and 22 and turns off the MOSFETs 13 and 23 from the time when the drive waveform feedback reaches the lower limit t2 to the time t4 when the pulse signal P1 from the pulse generation circuit 3 falls. , B2 is generated. That is, after a predetermined time (t1-t2) has elapsed after the MOSFETs 12 and 22 are turned off, the MOSFETs 12 and 22 are turned on and the MOSFETs 13 and 23 are turned off. The predetermined time (t1-t2) can also be said to be the time of the first half cycle of the vibration signal generated on the secondary side of the transformer 11 as described above. Thus, by turning off the MOSFETs 13 and 23 in the time (t2−t4), the current flowing from the piezoelectric elements 1a and 1b to the transformers 11 and 21 is cut off, and free vibration generated on the secondary side of the transformer is suppressed. As a result, power loss in the drive circuits 6 and 7 can be reduced, and optimal power can be supplied to the ultrasonic motor 1.
(2) Also, malfunctions caused by free vibration of the switching control circuits 4 and 5 can be prevented.

-Second Embodiment-
FIG. 6 is a diagram showing a configuration of an ultrasonic motor driving apparatus according to the second embodiment of the present invention. The ultrasonic motor driving apparatus according to the second embodiment includes a DC power supply circuit 2, a pulse generation circuit 3, switching control circuits 4, 5 and driving circuits 6a, 7a. The drive circuit 6 a includes a transformer 11, MOSFETs 12, 13 and 41, diodes 14, 15, 42 and 43, and an inverter 16. Similarly to the drive circuit 6a, the drive circuit 7a includes a transformer 21, MOSFETs 22, 23, 51, diodes 24, 25, 52, 53, and an inverter 26.

  The second embodiment is different from the first embodiment in that the MOSFET 41 and the diodes 42 and 43 are added to the primary circuit of the transformer 11 in the drive circuit 6a. In the drive circuit 7a, the MOSFET 51, The only difference is that the diodes 52 and 53 are added to the primary side circuit of the transformer 21. Components similar to those in the first embodiment are denoted by the same reference numerals.

  The switching control circuits 4 and 5 are also the same as in the first embodiment, but the gate terminals of the MOSFETs 41 and 51 added in the second embodiment with the signals A1 and A2 not used in the first embodiment. Has been entered.

  FIG. 7 is a timing chart for driving the ultrasonic motor 1 according to the second embodiment. This corresponds to FIG. 4 of the first embodiment. The operations of the drive circuit 6a and the drive circuit 7a are based on the same principle. Therefore, the operation in the drive circuit 6a, that is, the supply of signals to the piezoelectric element 1a will be described as a representative.

  As shown in FIG. 7A, the pulse generation circuit 3 outputs a pulse signal P1 having a desired frequency (period t1-t4). The switching control circuit 4 receives the pulse signal P1 and the drive waveform feedback signal from the primary side of the transformer 11 of the drive circuit 6, and receives the signal B1 shown in FIG. 7B and the signal A1 shown in FIG. 7C. Is output. The generation of the signal B1 and the signal A1 is as described in the first embodiment.

  The signal B1 is input to the gate terminal of the MOSFET 12 and the MOSFET 12 is turned off while the signal B1 is Low (t1-t2), and the MOSFET 12 is turned on while the signal B1 is High (t2-t4). Be controlled. On the other hand, the signal B1 is inverted by the inverter 16 and input to the gate terminal of the MOSFET 13, the MOSFET 13 is turned on while the signal B1 is low (t1-t2), and the MOSFET 13 is turned off while the signal B1 is high (t2-t4). The switching is controlled as follows.

  The signal A1 is input to the gate terminal of the MOSFET 41, the MOSFET 41 is turned on while the signal A1 is low (t1-t2, t3-t4), and the MOSFET 41 is turned on while the signal A1 is high (t2-t3). Switching control is performed to turn off. Although the MOSFETs 12 and 14 are Nch-MOSFETs, but the MOSFET 41 is a Pch-MOSFET, the on / off operation with respect to the gate signal is reversed.

  While the MOSFET 12 is on from t2 to t4, the current I1 tends to flow from the DC power supply circuit 2 to the primary winding of the transformer 11. However, the signal A1 turns off the MOSFET 41 between t2 and t3, and 1 of the transformer 11 No current flows in the next winding.

  As described in the first embodiment, as current flows through the primary winding of the transformer 11, the energy stored in the transformer 11 increases and the voltage applied to the piezoelectric element 1a also increases. However, even if the voltage applied to the piezoelectric element 1a is increased more than necessary, it only becomes thermal energy and is inefficient. Therefore, in order not to unnecessarily increase the voltage applied to the piezoelectric element 1a, the MOSFET 41 is turned off by the signal A1 so that no current flows through the primary winding of the transformer 11.

  FIG. 8 is a diagram showing a driving timing chart of the ultrasonic motor 1 when the driving frequency is increased. As the driving frequency is increased, the period t1-t4 becomes shorter. On the other hand, the time t1-t2 is constant because it is determined by a constant such as the inductance of the transformer. The time t3-t4 is also constant due to the duty ratio determined in advance in the pulse generation circuit 3. Therefore, when the drive frequency is increased and the cycle is shortened, the ON signal of the signal A1 eventually disappears and the MOSFET 41 is not turned off. FIG. 8 is a diagram showing this state.

  In the second embodiment, the MOSFET 12 is turned on (t2-t4) and the MOSFET 41 is turned off for a predetermined time (t2-t3) after a predetermined time (t1-t2) has elapsed after the MOSFET 12 is turned off. ing. The predetermined time (t2-t3) is determined in advance from the period (t1-t4) when the current (flow) is determined by circuit constants such as a transformer (t1-t2) and when the current needs to flow through the primary winding of the transformer 11. This is the remaining time obtained by subtracting the determined time (t3-t4). In the present embodiment, the time (t3−t4) is predetermined as a ¼ period. However, what is necessary is just to determine suitably so that the energy which should be given to the primary winding of the transformer 11 can be ensured.

  The operation on the drive circuit 7a side can also be described in the same manner using the timing charts of FIGS.

The ultrasonic motor driving device according to the second embodiment configured as described above has the following effects.
(1) Since the MOSFETs 41 and 51 are provided on the primary side of the transformers 11 and 21 and the energy stored in the primary windings of the transformers 11 and 21 is appropriately controlled, an unnecessarily high voltage is applied to the piezoelectric element 1a, There is no application to 1b. Further, the MOSFETs 12, 13, 22, and 23 are controlled in the same manner as in the first embodiment to appropriately control the energy stored in the primary windings of the transformers 11 and 21 while suppressing the occurrence of free vibration. As a result, in addition to the effects of the first embodiment, the power loss of the circuit is further reduced, and more optimal power of the ultrasonic motor can be supplied. FIG. 9 is a comparison diagram of input power characteristics of the ultrasonic motor 1 according to the related art, the first embodiment, and the second embodiment.

  In the above embodiment, the example of the rotary ultrasonic motor has been described. However, the present invention is not necessarily limited to this content. A linear ultrasonic motor in which the relative motion member moves linearly may be used.

  In the above-described embodiment, the example in which the piezoelectric element is polarized to 12 poles in the ultrasonic motor has been described, but it is not necessarily limited to this content. The form of polarization and the form of signal supply to each polarized piezoelectric element may be arbitrary. An individual piezoelectric element may be appropriately disposed. The vibrator may be a member other than the piezoelectric element. That is, the present invention can be applied to all ultrasonic motors having a vibrator and a relative motion member that is pressed against the vibrator and driven by the vibration of the vibrator. The ultrasonic motor is a concept including what is called a vibration wave actuator.

  In the above-described embodiment, an example in which two signals whose phases are shifted by 90 degrees is supplied to the vibrator of the ultrasonic motor has been described. However, the present invention is not necessarily limited to this content. The phase shift may have different values, and the number of signals may be three or more.

  In the above-described embodiment, the example in which the MOSFET is used as the switching element has been described, but it is not necessarily limited to this content. Transistors other than MOSFETs and other switching elements may be used.

  Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other embodiments conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

It is a figure which shows the structure of the ultrasonic motor drive device which is the 1st Embodiment of this invention. 2 is a diagram showing an internal configuration of a switching control circuit 4. FIG. It is a figure which shows the drive frequency versus rotational speed (rotation speed) characteristic of the ultrasonic motor. 2 is a timing chart for driving the ultrasonic motor 1. FIG. FIG. 5 is a diagram illustrating a timing chart of a process in which a signal B1 is generated in a switching control circuit 4. It is a figure which shows the structure of the ultrasonic motor drive device which is the 2nd Embodiment of this invention. It is a figure which shows the timing chart of the drive of the ultrasonic motor 1 of 2nd Embodiment. It is a figure which shows the timing chart of a drive of the ultrasonic motor 1 when a drive frequency is raised. It is a comparison figure of the input power characteristic of the ultrasonic motor 1 of a prior art, 1st Embodiment, and 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic motor 1a, 1b Piezoelectric element 2 DC power supply circuit 3 Pulse generation circuit 4, 5 Switching control circuit 6, 7 Drive circuit 11, 21 Transformer 12, 13, 21, 23, 41, 51 MOSFET

Claims (10)

An ultrasonic motor driving device that drives an ultrasonic motor having a vibrator and a relative motion member that is pressed against the vibrator and driven by the vibration of the vibrator,
A transformer for supplying a voltage from the secondary winding to the vibrator, connecting a DC power source to the primary winding;
First switching means for turning on and off the current flowing in the primary winding of the transformer;
Second switching means for turning on and off the current flowing in the secondary winding of the transformer;
Third switching means for turning on and off the current flowing in the primary winding of the transformer;
When the first switching means, the second switching means, and the third switching means are controlled to be turned on and off , and the first switching means is turned on, the third switching means is An ultrasonic motor driving device comprising switching control means for controlling to turn off for a period . The ultrasonic motor driving device according to claim 1,
The switching control means controls the first switching means to drive the ultrasonic motor by turning on and off at a predetermined cycle, and after turning off the first switching means within the predetermined cycle. An ultrasonic motor driving device that controls to turn off the second switching means after a predetermined time has elapsed. The ultrasonic motor driving device according to claim 1,
The switching control means controls the first switching means to drive the ultrasonic motor by turning on and off at a predetermined cycle, and after turning off the first switching means within the predetermined cycle. An ultrasonic motor driving apparatus, wherein after the predetermined time has elapsed, the first switching means is turned on and the second switching means is turned off. In the ultrasonic motor drive device according to any one of claims 1 to 3,
The ultrasonic motor driving apparatus according to claim 1, wherein the switching control unit controls the second switching unit to be turned off while the first switching unit is turned on. In the ultrasonic motor drive device according to any one of claims 1 to 4,
The ultrasonic motor driving apparatus according to claim 1, wherein the switching control unit controls the second switching unit to be on while the first switching unit is off. In the ultrasonic motor drive device according to any one of claims 1 to 5,
The ultrasonic motor driving device according to claim 1, wherein the predetermined period is shorter than a period during which the first switching means is on . The ultrasonic motor driving device according to claim 6,
The ultrasonic motor driving apparatus according to claim 1, wherein the predetermined period is a period after a predetermined time has elapsed since the first switching unit was turned on. In the ultrasonic motor drive device according to any one of claims 1 to 5 ,
Before SL switching control means, the control means controls so as to turn off said third switching means in said first switching means after turned on after a predetermined time has elapsed, while turning on the first switching means An ultrasonic motor driving device. An ultrasonic motor driving device that drives an ultrasonic motor having a vibrator and a relative motion member that is pressed against the vibrator and driven by the vibration of the vibrator,
A transformer for supplying a voltage from the secondary winding to the vibrator, connecting a DC power source to the primary winding;
First switching means for turning on and off the current flowing in the primary winding of the transformer;
Second switching means for turning on and off the current flowing in the primary winding of the transformer;
Switching control means for controlling on / off of the first switching means and the second switching means,
Said switching control means, said first switching means, and controls to drive the ultrasonic motor by turning on and off at a predetermined period, within said predetermined period, said first switching means a first after a predetermined period of time off, when the first switching means have a second predetermined period on controls to third predetermined time period off shorter than the second of said second predetermined period switching means An ultrasonic motor drive device characterized by that. In the ultrasonic motor drive device according to claim 9,
The ultrasonic motor driving apparatus characterized in that the switching control means turns off the second switching means for the third predetermined period from the time when the first switching means is turned on .

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