Buck Output Inductor Ripple Calculator
Calculate peak-to-peak inductor current ripple for a buck converter output choke. Verifies against inductor saturation current and output capacitor ESR.
How to Use
- Enter input voltage, output voltage, switching frequency, inductor value, and load current.
- Tool computes ΔI_L pp and peak inductor current to verify against I_sat.
Show Work
Formulas
History of Output Inductor Sizing
Middlebrook and Cuk's state-space averaging (1976) at Caltech gave power electronics engineers the rigorous framework for analyzing ripple, transient response, and stability of switch-mode converters. The rule-of-thumb target 20-40% inductor current ripple came from TI and National Semiconductor's application notes of the 1980s - balancing inductor size against output capacitor stress. Modern high-frequency GaN converters shrink output inductors to nH range, but the same ripple target guides component selection.
About This Calculator
Enter V_in, V_out, f_sw, inductor value L, and load current I_out. The tool computes duty cycle D = V_out/V_in, peak-to-peak ripple ΔI_L = V_out·(1-D)/(f·L), peak inductor current I_peak = I_out + ΔI_L/2, and checks against your datasheet I_sat.
For lowest ripple: increase L (larger, more expensive) or raise switching frequency. For production, specify I_sat ≥ 1.3·I_peak and I_rms ≥ I_out for thermal derating. Everything runs client-side.
About the Buck Output Inductor Ripple Calculator
Whether you are at a desk or on your phone, the Buck Output Inductor Ripple Calculator makes electronics and circuit design easy — and it is completely free. Calculate peak-to-peak inductor current ripple for a buck converter output choke. Verifies against inductor saturation current and output capacitor ESR.
How it works
Type your numbers into the boxes. The answer shows up right away — you do not have to press a button. If you change a number, the answer changes too. So you can try different numbers and watch what happens, or check an answer you worked out yourself. Just make sure each box has the right kind of number in it.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
Ripple rule of thumb?
Target ΔI_L ≈ 20-40% of full-load current. Too little ripple = large/expensive inductor; too much = need higher-current rating and more output cap.
CCM vs DCM?
Continuous-Conduction Mode (CCM): I_L never reaches zero, ripple overlays the DC current. DCM: I_L hits zero each cycle, higher ripple, different math. Most buck converters operate CCM at full load.
I_peak headroom?
Size inductor such that I_peak = I_out + ΔI_L/2 < 0.8·I_sat. 20% margin accounts for transient overshoot during load steps.
How do I use the Buck Output Inductor Ripple Calculator?
Simply type your numbers and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
12 V → 3.3 V Buck
V_in=12 V, V_out=3.3 V, f=500 kHz, L=4.7 µH, I_out=2 A: ΔI_L ≈ 1 A pp (50% ripple).
24 V → 5 V Industrial
Pick L for 30% ripple at max load. Lower-ripple designs: larger L, more cost.
5 V USB-PD 20 V output
Boost from 12 V to 20 V; different equation (boost, not buck).
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