Flyback Converter Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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When you need a quick flyback converter check, the useful number is the one you can reproduce. Circuit sizing becomes much clearer when the ideal equation is separated from practical constraints such as ripple, temperature, tolerances, surge, and component ratings. The goal is to make the equation, inputs, and result easy to sanity-check rather than hide them behind a black box.

What this calculator does

This calculator focuses on flyback duty cycle from Input voltage (Vin), Output voltage (Vout), Voltage on the rectifier (Vrect). It is designed for quick estimation and hand-checking, with the visible fields defining the scope of the model rather than implying a larger simulation.

How to use it

Start with Input voltage (Vin), Output voltage (Vout), Voltage on the rectifier (Vrect), Windings ratio (N), Output current (Iout). Let the unit controls handle supported conversions instead of converting values mentally. If the page offers both inputs and derived fields, fill the quantities you know and leave result fields for the calculator.

How the calculation works

The duty estimate is D = (Vout+Vrect)/(N·Vin+Vout+Vrect). From output current it estimates secondary and primary peak currents, switching period, and primary/secondary inductances using an idealized flyback relationship.

Example

With the default setup (Input voltage (Vin) = 24 V; Output voltage (Vout) = 12 V; Voltage on the rectifier (Vrect) = 0.7 V; Windings ratio (N) = 1), the page reports flyback duty cycle of 34.604905 %. Reproducing this default result is a quick way to verify units before replacing the values with your own case.

How to interpret the result

The flyback duty cycle belongs to the ideal relationship shown above. Keep voltage, current, frequency, impedance, duty cycle, and component units consistent, then compare the result with real component limits rather than using it as the limit itself.

Limitations and notes

Real circuits include switch and diode losses, ESR/ESL, ripple, tolerances, thermal limits, control-loop behavior, transients, electromagnetic interference, and manufacturer derating that ideal equations may not capture. The most important values to verify are Input voltage (Vin), Output voltage (Vout). The calculator is a compact model of the visible fields, not a replacement for measurement uncertainty, component data, governing standards, or a full numerical analysis when those are required.