A drive device for a piezoelectric actuator, wherein the time needed to achieve highly efficient drive conditions is shortened to reduce power consumption, and stabilized control can be performed. The device has a phase difference detection device (phase difference/voltage conversion circuit ( 51 )) for detecting detection signals of longitudinal oscillation and bending oscillation from an oscillator ( 5 ) and detecting the phase difference between these two signals, frequency control devices ( 52 to 56 ) for comparing the phase difference detected by the phase difference detection device with a standard phase difference value and controlling the frequency of a drive signal sent to a piezoelectric element ( 17 ) on the basis of the results of this comparison, and an amplitude detection device (amplitude detection circuit ( 57 )) for detecting the amplitude of the detection signal of the piezoelectric element ( 17 ). The frequency control device compares the amplitude with a standard amplitude value and controls the frequency of the drive signal on the basis of the results of this comparison.
展开▼
