The present invention provides a power supply arrangement with a DC-to-DC converter (10) for providing at least one supply voltage to a load (20, 30, 40) from an energy source (11). The converter comprises means for inputting (4) a battery voltage from the energy source to output a voltage in a predetermined battery voltage range and a transfer circuit (8) connected to said means for inputting, to convert the battery voltage to at least one supply voltage in such a way that the supply voltage will be opposite in polarity to the battery voltage and the absolute value of the supply voltage will be the same or close to the absolute value of the battery voltage. The arrangement also comprises means for controlling (2), connected to the means for inputting, to control the supply voltage independent from the battery voltage using a single converting mode for the supply voltage range. The advantage of the arrangement is to supply continuously and ripple-free to the load the supply voltage range independent from but opposite in polarity to the battery voltage.