Power Conversion / design models
Buck Converter Designer
Estimate duty cycle, inductor, output capacitor, ripple current, peak current, and estimated total power loss.
Answer first
How do I choose first-pass buck inductor and capacitor values?
This buck converter calculator turns input voltage, output voltage, load current, switching frequency, and ripple targets into first-pass inductor and capacitor values. It also estimates duty cycle, peak current, and power loss. Use the result to compare parts, then verify controller limits, transient response, saturation, thermal behavior, and layout with the selected datasheets.
Set your supply targets
Trace an operating phase
The highlighted path carries conventional current. Values follow your inputs.
The switch closes the source loop. Inductor current rises while the catch diode is reverse biased.
Ideal continuous-conduction model: zero switch and diode drop. Efficiency only estimates total loss; it does not alter ideal timing.
Output capacitance is a ripple-only minimum with zero ESR. Controller stability, load transients, bias derating and ripple-current ratings require separate checks.
Equations and model scope
This is an ideal asynchronous buck power stage in continuous conduction. It omits controller feedback, input decoupling and parasitics. Real duty, capacitor selection and regulation depend on the selected controller.
Design guide
Use the result with engineering context
Technical content reviewed
When this tool is useful
- Sizing an initial inductor from an allowed ripple-current target
- Estimating output capacitance from switching frequency and voltage ripple
What the result includes
- Ideal duty cycle, inductor value, ripple current, and peak current
- Output capacitance estimate and a first power-loss breakdown
What the model does not guarantee
- The capacitor calculation does not model the full impedance curve, aging, bias derating, or control-loop response
- The loss estimate cannot approve MOSFET temperature, inductor saturation, compensation, or PCB layout
Worked approach
Size from ripple, then check the parts
Choose a ripple-current fraction that the load and inductor can tolerate. Use the calculated inductance and peak current to shortlist parts, then check saturation current, DCR, core loss, capacitor ESR, and the controller's recommended range.
Common decisions
Questions engineers ask
Can I use the nearest standard inductor value?
Usually, but recalculate ripple and peak current with the actual value. A smaller inductor increases ripple and peak current; a larger one changes transient response and may cost more or occupy more area.
Why is the ceramic capacitor's printed value not enough?
Ceramic capacitance can fall under DC bias. Package size, dielectric, temperature, tolerance, and voltage rating determine how much capacitance remains in operation.
Does a correct calculation guarantee a stable converter?
No. Stability depends on the controller topology, compensation, output network, load range, layout, and the component models used by the manufacturer.
Related build evidence
Aqua Sync 2.0.0
Inspect a connected sensing system where firmware, displays, sensors, and board integration must work together. The project does not claim to use the converter values generated here.
See the projectApply it to real hardware
Building a battery or DC-powered device?
Share the voltage range, rails, current profile, noise limits, board area, and preferred controller so the power stage can be reviewed in context.
Discuss the system