| 摘要 |
PURPOSE:To achieve stable operation, by varying the sweeping speed based on variation of speed of a moving body thereby increase the speed of driving frequency control and carrying out frequency sweeping until phase difference is settled within a setting range. CONSTITUTION:In a drive circuit for a supersonic motor, a voltage controlled oscillator 7 oscillates according to the control voltage at a control terminal C1, and the output therefrom is splitted into two. One of them is applied from a 90 deg. phase shifter 9 to a power amplifier 10 while the other is applied through a power amplifier 11 onto a piezoelectric member 2. Current and voltage of the piezoelectric member 2 are detected through detectors 13, 12, then the phase difference is detected through a phase difference detector 14 and fed to a phase comparator 15. The comparator 15 compares an operation setting level P1 and an operation range level P2 to produce a control signal corresponding to the difference. The control signal is fed from a controller 16 as a sweep control signal for driving frequency to a voltage controlled oscillator 7 through an adder 8 in order to control the output frequency of the oscillator 7. Sweeping is carried out until the phase difference comes within range P2 surrounding the setting level P1. |
