Importance

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Abstract

A control circuit for an ultrasonic dental scaler, comprising a transducer driven by a frequency-controlled oscillator, is disclosed. The control circuit is operable for continuously regulating the oscillator frequency at substantially the same value as the resonant frequency of the transducer with a dental tool attached to it and for controlling the mechanical power output of the transducer. The transducer can be drivingly connected to a work tool for transmitting mechanical energy thereto. The regulation of the oscillator frequency is accomplished by simultaneously applied control signals derived from the current passing through the transducer and from the voltage across the transducer, to compensate for supply voltage variations. Moreover, the mechanical power output of the transducer is controlled such that it is reduced whenever the contact pressure of the work tool exceeds a predetermined maximum value. Such excessive pressure is monitored as the amplitude or phase variation of the voltage or of the current of the transducer.

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First Claim