Buck and Boost Converter Inductor Calculator
Find the inductance, duty cycle and peak current for a switching (DC-DC) regulator.
Formulas and cautions
Buck: D = Vout/Vin, L = (Vin − Vout)·D / (f·ΔI). Boost: D = 1 − Vin/Vout, inductor current IL = Iout/(1 − D), L = Vin·D / (f·ΔI). The converter is assumed lossless. Besides inductance, the inductor's saturation current rating must exceed the peak current, and the controller datasheet's recommendations take priority in a real design.
Frequently asked questions
How much ripple current should I design for?
20 to 40% of the average inductor current is the usual range. Less ripple needs a larger, more expensive inductor; more ripple raises the peak current and output ripple. 30% is a common starting point.
Why does the inductor's saturation current matter?
Above its saturation current an inductor's inductance collapses, current spikes and the converter can fail. Choose a part whose saturation rating is above the calculated peak current, with some margin.