| 摘要 |
PURPOSE:To obtain a driving circuit for an ultrasonic motor which can control a rotating speed by maintaining a state that the motor is driven in a high efficiency and has a small size and a low cost. CONSTITUTION:A frequency tracing circuit 28 so control that a frequency of a reference signal to be output from an oscillator 30 follows up an optimum driving frequency of an ultrasonic motor 12. A pulse-width modulator 14 modulates a pulse with of a reference signal output from the oscillator 30 in response to input speed set data, and outputs to power amplifiers 62, 64. The amplifiers 62, 64 supply ultrasonic motor drive signals of an amplitude responsive to a duty ratio of the input reference signal to the motor 12. |
