SMPS Design Calculators – Buck Converter Tools

Buck Converter Quick Calculators

These mini-calculators help with first-pass sizing for simple buck converters. They are not a replacement for full datasheet design procedures, but they give a fast starting point before you jump into SPICE or vendor design tools.

All formulas assume continuous conduction mode (CCM), ideal components, and simplified conditions. Always verify results with real datasheets and simulations.

1. Duty Cycle (Ideal Buck)

Input voltage V_IN [V] Output voltage V_OUT [V]

Ideal CCM buck: D ≈ V_OUT / V_IN. Real converters add losses, deadtime and slope compensation.

2. Inductor Value

V_IN [V] V_OUT [V] I_OUT [A] f_SW [kHz] ΔI_L [% of I_OUT]

Formula: L ≈ (V_IN − V_OUT) · D / (ΔI_L · f_SW) with D ≈ Vout/Vin.

3. Output Ripple (Capacitor Only)

I_OUT [A] f_SW [kHz] C_OUT [µF] Target ΔV_OUT [% of Vout]

Very simplified: ΔV ≈ I_OUT / (8 · f_SW · C_OUT) for triangular ripple. Does not include ESR/ESL effects.