This flyback converter calculator estimates duty cycle, peak currents, and ideal primary and secondary inductance for discontinuous transformer design.
Physics
Flyback Converter Calculator
Estimate ideal flyback duty cycle, peak currents, and winding inductances.
Calculator
About this calculator
Formula notes
duty = (output + rectifier drop) x turns ratio / (input + adjusted output); peak currents and inductances follow the standard flyback energy-transfer equations.
Worked examples
- Example: 12 V input, 5 V output, 0.5 V drop, 2:1 turns, 1 A output at 100 kHz gives duty about 47.8%, secondary peak near 3.83 A, and primary inductance about 29.9 uH.
- With 24 V input, 12 V output, 0.5 V rectifier drop, 1:1 turns, 2 A output at 50 kHz, the ideal duty cycle is about 34.2% and peak secondary current about 6.08 A.
How to use it
- Enter input and output voltages plus rectifier drop.
- Enter turns ratio, output current, and switching frequency.
- Review duty, peak currents, and inductance estimates.
Frequently asked questions
Does this cover boundary and continuous modes?
It assumes an idealized discontinuous-mode converter and omits losses, leakage, and control loop effects.
Can I rely on these for hardware?
Use it as initial calculations only, then validate with transformer specs, snubbing, EMI, and thermal considerations.
Limits and interpretation
- The ideal equations omit transformer leakage, core losses, switching losses, diode recovery, and control-loop dynamics.
- Calculate with margins and verify against real-world thermal, EMI, and saturation behavior before manufacturing.