In this paper, Smart Step-Down Convertor is introduced as a power supply to power a device which operates at a voltage below the power net voltage while protecting the power net and the device against faults as well. In the proposed architecture, each Smart Step-Down Converter is connected to the battery or the power source with the nominal voltage (e.g. 48V) and it provides a programmable output voltage that can be set to the rated voltage of the electric load coupled to it. The rated voltage of electric loads can be equal or lower than the nominal voltage. The proposed system with Smart Step-Down Converters has several advantages compared to other multi-voltage system architectures. First, the 12V battery and 12V power distribution box are eliminated, resulting in not only material savings but also solving some packaging challenges. Second, Smart Step-Down Converters enable downsizing the wire harnesses and amount of copper used in a vehicle since for a given delivered power, boosting the voltage proportionally reduces the required current and consequently, thinner wires can be used. Third, energy conversion is more efficient compared to the centralized topology, since each Step-Down Converter is designed to operate at its maximum efficient point at all time unlike a high power convertor, employed in a centralized topology, which operates in a wide power range depending on an amount of the current, it delivers. Fourth and the most important advantage is that Smart Step-Down Converters provide a great deal of flexibility for future upgrade. Any loads can easily be upgraded with the similar loads with a different operating voltage by just changing the associated Smart Step-Down Converters. This allows the electrical systems to take advantages of technology in future for example when a more efficient load with similar functions like its current counterpart is available but it requires non-standard voltage.