A DC-DC converter includes a first half-bridge circuit, a second half-bridge circuit, at least one transformer having at least one primary winding and at least one secondary winding, wherein the first and second half-bridge circuits are designed to generate an AC voltage at the at least one primary winding, and a rectifier circuit having an output terminal. The output terminal includes a first output terminal pole and a second output terminal pole. The rectifier circuit includes at least one rectifier element. The rectifier circuit is designed to rectify a voltage present at the at least one secondary winding and to output it at the output terminal. The rectifier circuit includes a polarity reversal protection transistor, the collector-emitter path of which or the drain-source path of which is looped in between a terminal of the at least one rectifier element and the first or the second output terminal pole of the output terminal.