Input circuit with polarity reversal and short circuit protection for a DC electricity supply or a switching regulator

The circuit (ES) has two potential connections (E1, E2) for connecting two low direct voltage potentials. A buffer circuit e.g. comparator (Kp) and p-channel FET (S2), comprises a buffer capacitor (C) buffers direct voltage. An inverse-polarity protection i.e. controllable switch (S1), is connected with the two connections. A control unit (AS) is opened in case of short-circuit of the potential connections or supply lines of the controllable switch. The control unit is provided with an inductor (L1) and two controllable switches (R1, R2, V1).