| 摘要 |
PROBLEM TO BE SOLVED: To detect phase difference between a vibration detecting signal and a driving signal without error, by making comparison levels of a first comparing means detecting the phase of an applied AC signal and a second comparing means detecting the phase of a detection signal, different from each other. SOLUTION: When a switch 20 for operation start turns on, a digital signal to be applied to a D/A converter 18 is swept from a specified value to a low value. According to it, the analog output voltage of the D/A converter 18 decreases, and the frequency of an output signal from a VCO circuit 21 decreases. The driving frequency of a A-phase and B-phase AC signal decreases, and the number of revolution of a vibrating motor 10 increases. According to increase of the number of revolution, the phase difference between an S-phase AC output signal for vibration detection and the A-phase AC driving signal increases. When the phase difference approaches a resonance phase difference value, a microcomputer 17 judges an output of a phase difference judgement circuit 16, controls the own parallel output port, and suspends sweep operation of a digital signal to be applied to a D/A converter 18. |
