In summary, the classifications of power switching topologies are the linear step-down configuration and a switching regulator which can be built to regulate higher or lower voltage, or to invert the polarity of the supply voltage. Whether it is a linear or switching voltage regulator, the basic need is to maintain a constant output voltage at a certain load. A voltage regulator works by comparing the output voltage to an internal reference, in a closed loop feedback circuit so that the output is kept at the set value, even with variations in input voltage or load. Linear regulators are limited to a step-down configuration; switching regulators can be built to regulate higher or lower voltage, or to invert the polarity of the supply voltage, by changing the position of the FET relative to the inductor and diode in the circuit. The ST eDesign Suite is a power supply simulation tool that facilitates the selection of devices and the design of DC/DC, AC/DC, LED drivers, and photovoltaic projects. It generates interactive schematics starting from the basic design specifications.