| 摘要 |
PROBLEM TO BE SOLVED: To provide a drive unit of an ultrasonic motor which is convenient in usage. SOLUTION: This drive unit 20 of an ultrasonic motor comprises an oscillation circuit 21, a phase comparison circuit 22, a filter circuit 23 and a phase synchronization loop circuit 25 consisting of a VCO(voltage-controlled oscillator circuit) 24. A phase difference between an oscillation frequency given to an A-phase terminal 12a and a common terminal 12c of a piezoelectric device 12 of the ultrasonic motor 11 by the oscillation circuit 21 and an oscillation frequency given to the B-phase terminal 12b, and the common terminal 12c from the VCO 24 is always kept at a constant value (90 deg.) by the phase synchronization loop circuit 25. Therefore, even if for instance, one of the oscillation frequencies is changed, the other oscillation frequency follows the change so as to keep the phase difference constant, so that it is not necessary to adjust the phase difference unlike the conventional constitution. |
