In a protective circuit for a converter having a plurality of phases, for each phase current of the phases, a signal proportional to the respective phase current is applied to a transformer circuit that, below and in the area of a limiting frequency, functions as a low-pass filter with the limiting frequency, and above the limiting frequency, functions as a divider. The outputs of the transformer circuit are applied to a maximum generator for forming the absolute value maximum. This maximum is fed to a comparator in which the maximum is compared to a reference value.