Boost Inductor Ripple Current

ΔIL = Vin · D / (fs · L)

Quick answer

This calculator solves ΔIL = Vin × D / (fs × L) for Ripple Current. With Input Voltage 12 V, Duty Cycle 50 %, Switching Frequency 100 kHz, Inductance 100 µH, the result is 0.6 A. It solves in 5 directions, so you can enter the values you have and get the one you need.

Calculator

Ripple Current (mA)
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Formula

ΔIL = Vin × D / (fs × L)

Description

During the switch on-time of a boost converter the full input voltage is applied across the inductor, ramping its current up. The peak-to-peak ripple equals the input voltage times the duty cycle (the fraction of the period the switch is on) divided by the switching frequency and inductance. It is the basic relationship for predicting inductor ripple from operating conditions.

Variables

  • ΔIL — Peak-to-peak ripple current (A)
  • Vin — Input voltage (V)
  • D — Switch duty cycle (0–1)
  • fs — Switching frequency (Hz)
  • L — Inductance (H)

Practical Notes

For a boost, D = 1 − Vin/Vout. Keep ripple in the 20–40% range of average current to balance core loss, RMS heating, and capacitor stress.

Symbols and units

Symbol Meaning Default unit Accepted units
dIL Ripple Current mA pA, nA, µA, mA, A, kA
Vin Input Voltage V pV, nV, µV, mV, V, kV
D Duty Cycle — —, %
fs Switching Frequency kHz Hz, kHz, MHz, GHz
L Inductance µH nH, µH, mH, H

Step by step

  1. 1. What you know: Input Voltage 12 V, Duty Cycle 50 %, Switching Frequency 100 kHz, Inductance 100 µH
  2. 2. The relation: ΔIL = Vin × D / (fs × L)
  3. 3. Substitute: Vin = 12 V, D = 50 %, fs = 100 kHz, L = 100 µH
  4. 4. Result: Ripple Current = 0.6 A

Related quantities from the same inputs

  • P = V × I = 7.2 W

Worked examples

Minimum range

Given: Input Voltage 0.33 V, Duty Cycle 2.5 %, Switching Frequency 100 Hz, Inductance 100 nH

Result: Ripple Current = 0.825 kA

Low range

Given: Input Voltage 3.3 V, Duty Cycle 25 %, Switching Frequency 1 kHz, Inductance 1 µH

Result: Ripple Current = 0.825 kA

Typical

Given: Input Voltage 12 V, Duty Cycle 50 %, Switching Frequency 100 kHz, Inductance 100 µH

Result: Ripple Current = 0.6 A

High range

Given: Input Voltage 0.23 kV, Duty Cycle 0.8, Switching Frequency 0.5 MHz, Inductance 0.47 mH

Result: Ripple Current = 0.783 A

Maximum range

Given: Input Voltage 2.3 kV, Duty Cycle 8, Switching Frequency 5 MHz, Inductance 4.7 mH

Result: Ripple Current = 0.783 A

Solving for each variable

Solve for Ripple Current

Input Voltage 0.33 V, Duty Cycle 2.5 %, Switching Frequency 100 Hz, Inductance 100 nH → 0.825 kA

Solve for Input Voltage

Ripple Current 100 µA, Duty Cycle 2.5 %, Switching Frequency 100 Hz, Inductance 100 nH → 40 nV

Solve for Duty Cycle

Ripple Current 100 µA, Input Voltage 0.33 V, Switching Frequency 100 Hz, Inductance 100 nH → 3.03 × 10⁻⁷ %

Solve for Switching Frequency

Ripple Current 100 µA, Input Voltage 0.33 V, Duty Cycle 2.5 %, Inductance 100 nH → 0.825 GHz

Solve for Inductance

Ripple Current 100 µA, Input Voltage 0.33 V, Duty Cycle 2.5 %, Switching Frequency 100 Hz → 0.825 H

How Ripple Current changes with Input Voltage

Input Voltage (input) Ripple Current (result)
1.2 V 60 mA
3 V 150 mA
6 V 0.3 A
9 V 0.45 A
12 V 0.6 A
18 V 0.9 A
24 V 1.2 A
48 V 2.4 A
84 V 4.2 A
120 V 6 A

The same result in other units

Unit Value
µA 600000
mA 600
A 0.6
kA 0.0006

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Frequently asked questions

How do you calculate Boost Inductor Ripple Current?

Use ΔIL = Vin × D / (fs × L). With Input Voltage 12 V, Duty Cycle 50 %, Switching Frequency 100 kHz, Inductance 100 µH, Ripple Current works out to 0.6 A.

What is the formula for Boost Inductor Ripple Current?

The formula is ΔIL = Vin × D / (fs × L). During the switch on-time of a boost converter the full input voltage is applied across the inductor, ramping its current up.

How do you find Input Voltage when you know the other values?

Rearrange for Input Voltage: with Ripple Current 100 µA, Duty Cycle 2.5 %, Switching Frequency 100 Hz, Inductance 100 nH, Input Voltage is 40 nV.

How do you find Duty Cycle when you know the other values?

Rearrange for Duty Cycle: with Ripple Current 100 µA, Input Voltage 0.33 V, Switching Frequency 100 Hz, Inductance 100 nH, Duty Cycle is 3.03 × 10⁻⁷ %.

What units does Boost Inductor Ripple Current use?

Ripple Current is shown in µA, mA, A, kA. Values are held in SI base units internally, so you can mix prefixes without converting by hand.

Related Concepts

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