Abstract: In a process and a circuit for exciting an ultrasonic generator the latter is excited by an output signal of a voltage-controlled oscillator, which is controlled by a control device including a triangular wave generator so that its frequency is periodically swept in a range covering the series resonance of the ultrasonic generator. A measured quantity value, which can be voltage or current corresponding to the damping of the ultrasonic generator, is formed and is compared with the maximum permitted damping. If the established damping is smaller than the maximum permitted damping, the oscillator is additionally regulated as a function of the measured quantity. This measured quantity is preferably a function of the exciting current of the ultrasonic generator. An instantaneous measured value and a delayed value are formed and their difference is compared with a threshold value in a comparator. If this difference is the same as the threshold value, the sweep direction in the control device is reversed.