Power Supply Ripple Calculator

Ripple voltage: calculation method

For this worksheet, the governing relationship is ΔV = I ÷ (C × ripple frequency). The entered quantities are Load current, Capacitance, and Ripple frequency.

The initial scenario returns 4.255 V. Re-enter field data before using the answer in a design or comparison.

Estimate capacitor-input supply ripple from load current, capacitance, and ripple frequency. For the companion required capacitance calculation, open Smoothing Capacitor Calculator.

Before entering values

Use voltage and current values from the same side of the transformer or converter. Nameplate and meter values are not interchangeable unless they describe the same condition.

Values used below a division bar must stay positive. Use the displayed unit for every field and document conversions separately. Continue with Motor Capacitor Calculator to evaluate required capacitance.

Load current

Default example: 2 A. Enter load current in A.

Capacitance

Default example: 4700 µF. Enter capacitance in µF.

Ripple frequency

Default example: 100 Hz. Enter ripple frequency in Hz.

Input quality checks

Values recorded at different operating points should not share one case.

Compare the magnitude with a quick independent estimate.

Checks before using the answer

This approximation excludes ESR, conduction angle, transformer regulation, and load transients.

Outside the entered variables, consider leakage inductance, parasitic capacitance, saturation, switching transients, and cooling. Document which effects were checked elsewhere in the analysis.

Record waveform, frequency, load level, and winding or device temperature.

A second scenario

Change Load current from 2 A to 2.4 A with the rest of the inputs held constant. The comparison runs from 4.255 V to 5.106 V.

Use a separate scenario when multiple conditions change together.

A practical checking sequence

Check the source of ripple frequency before calculating. A credible result requires every field to describe the same physical condition and unit basis.

After calculating ripple voltage, compare its magnitude with component ratings and isolation requirements. An independent order-of-magnitude check can reveal a misplaced decimal or unit prefix.

Document any effect handled outside this page, especially diode loss, ESR, regulation, ripple current, and thermal resistance. That note prevents a later reader from assuming the simple equation covered it.

Before relying on the answer