How to Calculate an Inductor for a SEPIC Converter

Learn how to calculate the right inductor into a circuit for an efficient SEPIC converter in this blog post.

Two Ways to Calculate SEPIC Converter Inductors

In order to design an efficient SEPIC converter, it is crucial to design the right inductor into a circuit.

It is best to do this with a practical example: The SEPIC converter, in the case of Wurth Electronics Midcom, has a flexible input of 5-24 V and needs to deliver a stable 12 V output. The current output is 0.7 A with a calculated ripple of 20%.

There are always two ways to calculate the inductor for the SEPIC converter. First is to calculate the formula of an inductor for switching regulators. Second--and what we recommend--is to use REDEXPERT.

Coupled Inductor vs. Single Inductors

After calculating the SEPIC converter topology, the program suggests the inductors that best fit electronically into the circuit. This list can then be further optimized by taking DCR or mechanical dimensions into consideration.

In this example, a coupled inductor pre-setting shows an example using two single inductors. The inductance value of the coupled inductor is exactly half of the single inductor. This clearly shows that by choosing a coupled inductor, the DCR can be reduced significantly (67 mOhm vs. two 72 mOhm).

All products shown in the inductor selector tool are catalog products. For Wurth Electronics Midcom, this means they are all available in stock, have short lead times for production volume, and offer outstanding quality.

Get started with designing coupled inductors for SEPIC converters by accessing the Component Selector tool or browsing our online catalog. To watch the entire training video, visit our company page on

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