| 摘要 |
PURPOSE:To easily perform the delicate adjustment of output amplitude by changing the output amplitude of an ultrasonic oscillator linearly corresponding to the manipulated variable of a variable adjusting means. CONSTITUTION:The triangular waves (C), (D) of half-wave rectifier circuits 3A, 3B are inputted to a comparator(CM) 5a. Meanwhile, no linear relation is found in the relation of the manipulated variable of the knob of a rotary encoder 4a and the output amplitude of the ultrasonic oscillator 10. Therefore, a ROM 4b receives the information of the kind of the ultrasonic oscillator 10, and selects a table fitting in each ultrasonic oscillator, and varies the resistance value of an electronic volume 4a nonlinearly. The CM 5a outputs a pulse signal for the triangular wave (F) (shown in dotted line) to which half-wave rectification is applied by a share exceeding a reference voltage Vref. Therefore, the CM 5a varies the duty factor of the pulse signal corresponding to the change of the reference voltage Vref, and outputs it to the gate of a FET 7a via buffer circuits 6A, 6B as a linear control signal. An AC pulse wave is supplied to the ultrasonic oscillator 10 from the secondary side of a step-up transformer 8. |
