Forward converter
Single-switch, two-switch and active-clamp forward transformer reset and CCM output-filter sizing.
Development preview. Check the assumptions below before relying on a result. Calculations run in your browser.
How it calculates
Assumptions
- Ideal CCM forward stage; output rectifier and winding drops are omitted.
- Active-clamp switch voltage follows ideal volt-second balance VIN/(1−D). Magnetizing current is reported as a rise; peak-current estimate assumes zero initial magnetizing current and is conservative for centered active-clamp current.
- Single-switch reset winding must fully demagnetize before the next cycle. Leakage spikes, reset diode stress and active-clamp resonance are not included.
Worked example
These are the calculator's default inputs. Change any input above to recalculate.
Inputs
- Primary reset
- single
- Minimum input
- 36 V
- Nominal input
- 48 V
- Maximum input
- 72 V
- Output voltage
- 12 V
- Output current
- 3 A
- Secondary / primary turns
- 0.75
- Reset / primary turns
- 1
- Switching frequency
- 150000 Hz
- Primary magnetizing inductance
- 0.002 H
- Output inductance
- 0.0001 H
- Effective output capacitance
- 0.00022 F
- Output ESR
- 0.02 Ω
- Controller maximum duty
- 0.45
Results
- Nominal duty
- 0.333333
- Reset/controller duty ceiling
- 0.45
- Nominal reset time
- 0.00000222222 s
- Magnetizing current rise
- 0.0533333 A
- Maximum switch peak
- 2.53667 A
- Maximum ideal switch voltage
- 144 V
- Nominal output-inductor ripple
- 0.533333 A
- Nominal output ripple
- 0.0126869 V