The present disclosure relates to a power supply unit having: an output for outputting an output current and an output voltage; and a protective element having a signal output path, wherein the protective element is connected downstream of the output and designed to maintain the signal output path when the output current exceeds a first amplitude threshold value and to interrupt the signal output path when the output current exceeds a second amplitude threshold value, the second amplitude threshold value being higher than the first amplitude threshold value; wherein the power supply unit is designed to reduce an amplitude of the output voltage and to increase an amplitude of the output current above the second amplitude threshold value, in order to interrupt the signal output path, when the output current exceeds the first amplitude threshold value.