What is the duty cycle formula for a boost converter?

For an ideal boost converter operating in continuous conduction mode (CCM), D = 1 − Vin / Vout. A 5 V → 12 V design runs at about 58.3% duty cycle.

What is the inductor current ripple and why does it matter?

Ripple current ΔIL = Vin × D / (L × f) is the peak-to-peak swing of current through the inductor each cycle. High ripple increases core losses, EMI, and peak switch current; low ripple requires a larger inductor.

How do I choose the inductance value?

A ripple ratio ΔIL / Iin of 20–40% is typical. Rearrange: L = Vin × D / (f × ΔIL). Higher switching frequency allows smaller L with the same ripple.

What is the peak switch current?

The switch (MOSFET or BJT) must handle I_pk = Iin + ΔIL / 2, where Iin = Iout / (1 − D). This is the key value for selecting a FET with adequate current rating and low Rds(on).

Does this account for switch and diode voltage drops?

No — this is an ideal first-order approximation. Real designs add the diode forward voltage to Vout and the FET on-state drop to Vin for a more accurate duty cycle and efficiency estimate.

What happens in discontinuous conduction mode (DCM)?

If your inductance is below the critical value for a given load, the inductor current reaches zero before each new cycle (DCM). The duty-cycle formula changes in DCM, and peak currents are higher. This calculator assumes CCM; verify your ripple ratio is below 200% to stay in CCM.

Boost Converter Calculator

Name: Boost Converter Calculator
Availability: InStock
Author: Nham Vu

Enter input voltage, output voltage, load current, switching frequency, and inductance to get duty cycle, inductor ripple, and capacitor requirements for your boost converter.

Converter Parameters

Input Voltage V_in (V)

Output Voltage V_out (V)

Load Current I_out (A)

Switching Frequency f_sw (kHz)

Inductance L (μH)

Max Output Voltage Ripple ΔV_out (mV)

Duty Cycle

—

D = 1 − V_in / V_out

Inductor Ripple ΔI_L

—

V_in · D / (L · f)

Peak Switch Current

—

I_in + ΔI_L / 2

Min Output Capacitor

—

I_out · D / (f · ΔV_out)

Design Breakdown

Parameter	Value	Formula
Enter parameters and click Calculate

Inductor Current Waveform

Triangular ripple in continuous conduction mode (CCM). Peak = I_in + ΔI_L/2, valley = I_in − ΔI_L/2.

Summary

Enter input voltage, output voltage, load current, switching frequency, and inductance to get duty cycle, inductor ripple, and capacitor requirements for your boost converter.

How it works

Enter the input voltage (Vin) and desired output voltage (Vout). Vout must exceed Vin.
Enter the load current (Iout) and switching frequency (typically 50 kHz – 2 MHz).
Provide your chosen inductance value (L) to calculate the resulting ripple current.
The duty cycle is computed as D = 1 − Vin / Vout (ideal, continuous conduction).
Inductor ripple current ΔIL = Vin × D / (L × f) shows how much current swings each cycle.
Minimum output capacitor C = Iout × D / (f × ΔVout) is sized to hold ripple within spec.

Use cases

Boosting a single-cell Li-ion battery (3.7 V) to 5 V for USB output.
Deriving a higher rail from a 12 V bus for analog circuits requiring 24 V.
Selecting inductors and capacitors for SMPS prototypes.
Verifying component values against a boost regulator IC datasheet.
Teaching power electronics — seeing how frequency and inductance trade off.
Quick sanity-check before running a full SPICE simulation.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu