Before going in detail about couple inductors for SEPIC converters, a SEPIC converter must be defined. SEPIC stands for Single Ended Primary Inductance Converter, and this circuit offers the possibility to use the function of a buck and boost regulator in one circuit. A buck converter regulates a high voltage into a smaller voltage, so input voltage is greater than output voltage. For example, like a car charger for a cell phone, 12V is converted down to 5V. A boost converter regulates a small voltage into a higher voltage, so input is smaller than output voltage. As an example: an LED driver with a 3V input converts to a 9V output. A SEPIC converter combines those functions and allows a circuit to have flexible input voltages with a stable output voltage.This type of converter can also be described as a Buck/Boost Converter.