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Forward Converter Calculator

Use the forward converter calculator to find the output voltage and the ripple current of your forward converter circuit.

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Duty cycle50%D = V_out ÷ (N·V_in) — the ideal continuous-conduction value, before switch and diode drops
Conversion ratio0.25×stepping down
Switching period4 µs
On time2 µs
Off time2 µs
Output power24 W
Input power26.6667 Wat 90% efficiency
Input current555.5556 mALESS than the output current — a buck trades voltage for current, which is why it is not a linear regulator
Power dissipated2.6667 Was heat in the switch, diode and inductor
Inductor ripple current1.5319 A76.6% of the output current — 20 to 40% is the usual design target
Peak inductor current2.766 Awhat the inductor and switch must actually be rated for — sizing on the average current undersizes them
Minimum current for continuous conduction765.9574 mAyou are in continuous conduction, so the duty-cycle formula above is valid
Inductance for 30% ripple120 µH
At twice the switching frequencyhalf the rippleripple is inversely proportional to both frequency and inductance, which is the trade that sets converter size — faster switching allows a smaller inductor but costs switching losses

The formula

buck D = V_out/V_in; boost D = 1 − V_in/V_out

Each topology has its own relation

A buck converter's duty cycle is simply the voltage ratio; a boost converter's is one minus the inverse ratio. They are not interchangeable — applying the buck formula to a step-up conversion gives a duty cycle above 1, which is why this page refuses the combination rather than returning a meaningless number.

All these relations assume continuous conduction and ideal components. A real converter needs a somewhat larger duty cycle, because the switch and diode each drop a few tenths of a volt and the inductor has resistance. Below a critical load the inductor current reaches zero each cycle, the converter enters discontinuous mode, and the duty cycle stops following the simple formula altogether — which is why the minimum continuous-conduction current is reported.

The peak inductor current, not the average, is what sizes the inductor and the switch. With 40% ripple the peak is 20% above the output current, and a component chosen on the average figure will saturate.

Ripple is inversely proportional to both frequency and inductance, which sets the central trade in converter design: switching faster allows a physically smaller inductor, at the cost of switching losses that rise with frequency.