A method for operating a DC-DC voltage converter apparatus having a plurality of DC-DC voltage converter units connected in parallel in an electrical network is provided. The DC-DC voltage converter units are operated in a master/slave configuration based on current mode control in order to set a desired output voltage. Here, a reference voltage, to which the output voltage is intended to be adjusted, for the slave converters is determined by way of a preconditioning function according to a predetermined calculation specification from a master reference voltage prescribed by the master converter. Stable control can therefore be ensured even in the case of fluctuating loading at the respective DC-DC voltage converter units.