These extremely compact DC-DC converters incorporate all necessary input and output filters, signaling and protection features, which are required in the majority of applications. The converters provide important advantages, such as flexible output power through total current limitation, extremely high efficiency, excellent reliability, very low ripple and RFI noise levels, full input-to-output isolation, negligible inrush current, soft start, over temperature protection, interruption time, and input over- and undervoltage lockout. The converters are particularly suitable for rugged environments, such as railway applications. They have been designed in accordance with the European railway standards EN 50155 and EN 50121-3-2. All printed circuit boards are coated with a protective lacquer. The converter covers a total input voltage range from 12.5 to 154 VDC in the same model. The input is protected against surges and transients occurring on the source lines. The outputs are continuously open- and shortcircuit proof.