Free DC-DC Buck Converter Inductor Calculator
Calculate minimum inductance, inductor ripple current, peak saturation current, and output capacitor ESR for continuous conduction step-down converters.
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Frequently Asked Questions
What happens if my inductor value is too small in a buck converter?
If inductance is too low, the ripple current (ΔIL) becomes excessive. This results in high peak currents that can saturate the inductor, higher peak-to-peak output voltage ripple, elevated AC core losses, and premature entry into discontinuous conduction mode (DCM) at moderate loads.
Why does capacitor ESR dominate buck converter output ripple?
At modern switching frequencies (500 kHz to 2 MHz), the output voltage ripple ΔVout is dominated by the inductor ripple current flowing through the capacitor equivalent series resistance (ESR): ΔVout ≈ ΔIL × ESR. Low-ESR multi-layer ceramic capacitors (MLCCs like X7R or X5R) or conductive polymer aluminum capacitors are essential.
What is the difference between CCM and DCM?
In Continuous Conduction Mode (CCM), inductor current never drops to zero during the switching cycle (Ivalley > 0). In Discontinuous Conduction Mode (DCM), the inductor completely discharges its stored energy before the next cycle starts, causing the switch node to ring and the duty cycle relationship to change based on load.
How does switching frequency affect buck converter inductor size?
Inductance is inversely proportional to switching frequency (L ∝ 1/fsw). Doubling the switching frequency from 250 kHz to 500 kHz halves the required inductance and magnetic core volume. However, higher frequencies increase switching losses in the MOSFETs and AC core losses.