Abstract: A microprocessor-controlled DC-DC converter includes a controllable switch for generating at least one output voltage (Ua). The duty cycle of the controllable switch is controllable depending upon the output voltage. Despite the use of an inexpensive and hence "slow" microprocessor, the control stability of the DC-DC converter will still be adequate if, during the computation time of the microprocessor that is available for the calculation of the duty cycle of the controllable switch, the output voltage is sampled more than once. The duty cycle of the controllable switch is presettable as discrete values (Df) determined by means of an output unit of the microprocessor. These discrete values are formed, from the respective duty cycle determined, by a coarse quantization which corresponds to the temporal resolution of the microprocessor and by a fine quantization associated with each quantization step of the coarse quantization.