Capacitor Ripple Voltage

ΔV = I / (2 × f × C)

Quick answer

This calculator solves ΔV = I / (2 × f × C) for Ripple Voltage. With Load Current 2 A, Ripple Frequency 1 kHz, Capacitance 100 µF, the result is 10 V. It solves in 4 directions, so you can enter the values you have and get the one you need.

Calculator

Ripple Voltage (mV)
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Formula

ΔV = I / (2 × f × C)

Description

In a full-wave rectifier or switching converter, the output capacitor charges during each half-cycle and discharges into the load between charge pulses. The peak-to-peak ripple voltage depends on the load current, the ripple frequency (twice the mains frequency for full-wave, or the switching frequency for SMPS), and the capacitance. Reducing ripple requires larger capacitance, higher switching frequency, or lower load current. This is the primary formula for sizing output filter capacitors in power supplies.

Variables

  • ΔV — Peak-to-peak ripple voltage (V)
  • I — DC load current (A)
  • f — Ripple frequency (Hz)
  • C — Filter capacitance (F)

Practical Notes

For a half-wave rectifier, use f (not 2f) as the ripple frequency equals the mains frequency. In switching converters, ESR contributes additional ripple: V_ESR = I_ripple × ESR. The total ripple is approximately √(ΔV² + V_ESR²). Use low-ESR capacitors (ceramic or polymer) when ESR ripple dominates.

Symbols and units

Symbol Meaning Default unit Accepted units
dV Ripple Voltage mV pV, nV, µV, mV, V, kV
I Load Current A pA, nA, µA, mA, A, kA
f Ripple Frequency Hz Hz, kHz, MHz, GHz
C Capacitance µF pF, nF, µF, mF, F

Step by step

  1. 1. What you know: Load Current 2 A, Ripple Frequency 1 kHz, Capacitance 100 µF
  2. 2. The relation: ΔV = I / (2 × f × C)
  3. 3. Substitute: I = 2 A, f = 1 kHz, C = 100 µF
  4. 4. Result: Ripple Voltage = 10 V

Related quantities from the same inputs

  • P = V × I = 20 W

Worked examples

Minimum range

Given: Load Current 2 mA, Ripple Frequency 5 Hz, Capacitance 100 nF

Result: Ripple Voltage = 2 kV

Low range

Given: Load Current 20 mA, Ripple Frequency 50 Hz, Capacitance 1 µF

Result: Ripple Voltage = 0.2 kV

Typical

Given: Load Current 2 A, Ripple Frequency 1 kHz, Capacitance 100 µF

Result: Ripple Voltage = 10 V

High range

Given: Load Current 100 A, Ripple Frequency 20 kHz, Capacitance 1 mF

Result: Ripple Voltage = 2.5 V

Maximum range

Given: Load Current 1 kA, Ripple Frequency 0.2 MHz, Capacitance 10 mF

Result: Ripple Voltage = 0.25 V

Solving for each variable

Solve for Ripple Voltage

Load Current 2 mA, Ripple Frequency 5 Hz, Capacitance 100 nF → 2 kV

Solve for Load Current

Ripple Voltage 10 mV, Ripple Frequency 5 Hz, Capacitance 100 nF → 10 nA

Solve for Ripple Frequency

Ripple Voltage 10 mV, Load Current 2 mA, Capacitance 100 nF → 1 MHz

Solve for Capacitance

Ripple Voltage 10 mV, Load Current 2 mA, Ripple Frequency 5 Hz → 20 mF

How Ripple Voltage changes with Load Current

Load Current (input) Ripple Voltage (result)
0.2 A 1 V
0.5 A 2.5 V
1 A 5 V
1.5 A 7.5 V
2 A 10 V
3 A 15 V
4 A 20 V
8 A 40 V
14 A 70 V
20 A 100 V

The same result in other units

Unit Value
mV 10000
V 10
kV 0.01

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Frequently asked questions

How do you calculate Capacitor Ripple Voltage?

Use ΔV = I / (2 × f × C). With Load Current 2 A, Ripple Frequency 1 kHz, Capacitance 100 µF, Ripple Voltage works out to 10 V.

What is the formula for Capacitor Ripple Voltage?

The formula is ΔV = I / (2 × f × C). In a full-wave rectifier or switching converter, the output capacitor charges during each half-cycle and discharges into the load between charge pulses.

How do you find Load Current when you know the other values?

Rearrange for Load Current: with Ripple Voltage 10 mV, Ripple Frequency 5 Hz, Capacitance 100 nF, Load Current is 10 nA.

How do you find Ripple Frequency when you know the other values?

Rearrange for Ripple Frequency: with Ripple Voltage 10 mV, Load Current 2 mA, Capacitance 100 nF, Ripple Frequency is 1 MHz.

What units does Capacitor Ripple Voltage use?

Ripple Voltage is shown in mV, V, kV. Values are held in SI base units internally, so you can mix prefixes without converting by hand.

Related Concepts

All Capacitors formulas →
Capacitive Reactance RC Time Constant Capacitor Energy Capacitor Charge Series Capacitance Parallel Capacitance Capacitor Impedance with ESR Capacitor Ripple Voltage

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