Forward Converter Calculator

What Is a Forward Converter?

A forward converter is an isolated DC/DC topology that transfers energy from input to output while the switch is on. A transformer provides galvanic isolation and sets the voltage ratio through its turns. Designers use it when they need regulated output voltage and isolation from the input bus.

Output Voltage and Ripple

$$V_{out} = \frac{D}{N} V_{in}, \quad N = \frac{N_p}{N_s}$$ $$I_{ripple} = \frac{D(1-D)}{N \cdot L \cdot f_s} V_{in}$$

$D$ is duty cycle (0 to 1), $N_p$ and $N_s$ are primary and secondary turns, $L$ is inductance in henries, and $f_s$ is switching frequency in hertz. Example: 48 V input, D = 0.4, N = 2 gives $V_{out} = 0.4/2 \times 48 = 9.6$ V.

Design Notes

Higher duty cycle raises output voltage but also increases volt-second stress on the transformer. Ripple current grows when inductance or frequency drops. Size the magnetics and filter capacitor for the expected ripple and load current.

Frequently Asked Questions

What is the turns ratio N?

N = N_p / N_s, the ratio of primary to secondary transformer turns. It scales how much input voltage appears at the output for a given duty cycle.

Why does ripple current matter?

Ripple current determines inductor size, core losses, and output capacitor RMS current. Excessive ripple can overheat magnetics and reduce efficiency.

Can duty cycle exceed 50% in a forward converter?

Two-switch and active-clamp variants allow higher duty cycles. Classic single-switch forward designs often limit D to avoid transformer saturation without a reset winding.

What units should I use for inductance and frequency?

Enter inductance in microhenries (µH) and switching frequency in kilohertz (kHz). The calculator converts to henries and hertz internally.

How is a forward converter different from a flyback?

A forward converter transfers energy directly while the switch is on. A flyback stores energy in the transformer and delivers it when the switch turns off.

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What Is a Forward Converter?

Output Voltage and Ripple

Design Notes

Frequently Asked Questions

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