Switching regulators for voltage conversion usually use inductors to store energy temporarily. These inductors are usually very large in size and must be positioned in the printed circuit board (PCB) layout of switching regulators. This task is not difficult because the current through the inductor may change, but not instantaneously. It may be continuous and usually relatively slow.
The switching regulator switches current back and forth between two different paths. This switching is very fast, and the specific switching speed depends on the duration of the switching edge. The path through which switching current flows is called thermal loop or AC current path, which conducts current in one switching state and does not conduct current in the other switching state. In the PCB layout, the thermal circuit area shall be small and the path shall be short, so as to minimize the parasitic inductance in these wiring. Parasitic wiring inductance can cause unwanted voltage offset and electromagnetic interference (EMI).