How this calculator works
An ideal buck stage applies the input to the inductor during switch-on and freewheels during switch-off. Average inductor voltage is zero at steady state, giving a duty-weighted output. The ripple relation sizes the inductance for a stated peak-to-peak current change. Continuous conduction and negligible switch and diode drops are assumed.
Formula
Vo = Vi D; D = Vo/Vi; L = (Vi-Vo)D/(fs deltaI).
Worked example
Reducing 12 V to 3 V needs D = 0.25. At 100 kHz and 0.3 A ripple, the required inductance is 0.000075 H.
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Frequently asked questions
Does this include efficiency?
No. It uses an ideal power stage. Real semiconductor drops, winding resistance and switching losses alter the required duty cycle.
What does ripple current mean?
The entered ripple is the difference between maximum and minimum inductor current within one switching cycle.
Can this model discontinuous conduction?
No. If current reaches zero for part of the cycle, conversion ratio also depends on the load. Check the conduction mode and controller limits separately.