| 摘要 |
PURPOSE:To prevent the overcurrent state of an ultrasonic vibrator from developing at the time when the power supply is put to work by a method wherein the control of a bias voltage supplied to the active elements of an oscillating part from a bias control part is strengthened. CONSTITUTION:The charging to a capacitor and active switching elements such as transistor and the like are utilized in combination. Concretely, the bias voltage supplying to the active elements of an oscillating part 6 is cut-off by switching the active elements by means of a charging current, which starts to flow to a capacitor at the time P, when the power supply is put to work. When the bias voltage is below the level L, the current, which flows across an ultrasonic vibrator 3, is also cut-off as shown by the wave form E in the attached figure, resulting in effectively preventing the overcurrent state of the ultrasonic vibrator from developing at the time when the power supply is put to work. |
