Electrical & Electronics

Buck & Boost Converter Calculator

Size or check a buck or boost converter inductor, estimate current and output ripple, and compare capacitor and power requirements.

Your inputs

Converter type

Inductor calculation

Input voltage · V

Target output voltage · V

Load current · A

Frequency · kHz

Target current ripple / average · peak-to-peak · %

Estimated efficiency · %

Capacitance · µF

Capacitor ESR · mΩ

Allowed output ripple · peak-to-peak · mV

Ideal CCM duty and component estimates. Efficiency only adjusts input power/current and total loss. Actual switch drops, control limits and DCM need a device-specific model.

Ripple sizing only; allow for transient loads, DC bias, tolerance and temperature. Follow the controller’s capacitor and compensation requirements.

TI SLVA477 · TI SLVA372

Your results

Duty cycle: —

Inductance: —

Inductor ripple · CCM estimate: —

Ideal average inductor current: —

Ideal peak inductor current: —

Ideal RMS inductor current: —

Minimum output capacitance · ripple only: —

Estimated output ripple · peak-to-peak: —

Ripple from ESR: —

Input current: —

Output power: —

Estimated total power loss: —

Ideal inductor current over one switching period

Formula—

Separate converter ripple estimates from power accounting

Design or analyse an ideal buck or boost power stage in continuous conduction. Estimate inductance, currents and output ripple. Efficiency affects input power and loss only; it does not correct the ideal duty cycle or inductor-current model.

Step by step

Choose buck or boost and design or analyse mode. Enter input, output, load and switching frequency.
Enter target current ripple or existing inductance, output capacitance, ESR, allowed voltage ripple and assumed efficiency.
Check conduction mode before interpreting current and capacitor results. Compare estimated ripple with the target.

Settings and limits

Conduction mode: The CCM model requires a positive inductor-current valley. At the boundary or in discontinuous conduction, detailed current and capacitor predictions are hidden.
Capacitance and ESR: Both capacitive ripple and ESR contribute to the estimate. Increasing capacitance cannot remove an excessive ESR contribution.
Efficiency assumption: Efficiency sets estimated input power and loss. Real duty, current peaks and losses require device-specific checks.

Worked example

Use the buck design example below. The computed inductance keeps the model in CCM and meets the voltage-ripple target.

Example input

Vin = 12 V; Vout = 5 V; Iout = 2 A
fs = 200 kHz; η = 90%; ΔIL / IL,avg = 30%
Cout = 100 µF; ESR = 20 mΩ; ΔVtarget = 50 mV

Expected result
D / L / I / V / P	≈
D	41.666667%
L	24.305556 µH
ΔIL	0.6 A
IL,avg	2 A
IL,pk	2.3 A
IL,rms	2.007486 A
Cout,min	9.868421 µF
ΔVESR	12 mV
ΔVout	15.75 mV
Iin	0.925926 A
Ploss	1.111111 W

In analyse mode, a much smaller inductance can leave CCM. Missing detailed results then indicate a model limitation.

Questions and troubleshooting

Why must input and output differ?

Buck requires input above output; boost requires output above input. This tool does not model a combined buck-boost topology.

Why is minimum capacitance unavailable?

Check conduction mode and ESR. Outside CCM, or when ESR alone consumes the ripple allowance, this model gives no capacitance solution.

Does this complete a converter design?

No. Verify switch limits, inductor saturation, capacitor bias, control-loop stability, layout and thermal performance with the chosen device.