Abstract: The invention relates to a method for operating a DC-DC converter for supplying an electrolysis device with electrical operating power, in which in a step at least four controllable semiconductor switching elements in an H-bridge arrangement with interphase transformers connected downstream are controlled by a predetermined control signal sequence for direct conversion of an electrical input DC voltage into an electrical output DC voltage. At least two DC voltage converter units are used, each having four controllable semiconductor switching elements in an H-bridge arrangement with interphase transformers connected downstream, the following steps being carried out: detecting a number of the DC voltage converter units, and adapting the control signal sequence to the detected number of DC voltage converter units.