What is the formula for Boost Output Capacitor?

The Boost Output Capacitor formula is Cout = Iout × D / (fs × ΔVout), where Cout—Output capacitance (F); Iout—Output current (A); D—Duty cycle (0–1); fs—Switching frequency (Hz); ΔVout—Allowed output ripple (V).

What does Cout mean in the Boost Output Capacitor formula?

Cout is Output capacitance (F).

Boost Output Capacitor

Q: How do you calculate Boost Output Capacitor?

Use the formula Cout = Iout × D / (fs × ΔVout). In a boost converter the output capacitor alone supplies the load during the switch on-time, when the inductor is disconnected from the output. Enter the values you know in the calculator above and it solves for the remaining variable.

Cout = Iout · D / (fs · ΔVout)

Calculator

Output Capacitance

Output Current

Duty Cycle

Switching Frequency

Output Ripple

Result

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Formula

Cout = Iout × D / (fs × ΔVout)

Description

In a boost converter the output capacitor alone supplies the load during the switch on-time, when the inductor is disconnected from the output. This formula sizes the capacitor for an allowed output ripple voltage. Boost outputs are inherently noisier than buck outputs because of this pulsed delivery, so the capacitor (and its ESR) dominates output ripple.

Variables

Cout — Output capacitance (F)
Iout — Output current (A)
D — Duty cycle (0–1)
fs — Switching frequency (Hz)
ΔVout — Allowed output ripple (V)

Practical Notes

This counts only the capacitive ripple; ESR adds ΔV = ΔIL_peak × ESR on top. Use low-ESR ceramics or parallel capacitors to meet a tight ripple spec.

Related Concepts

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