Forward Converter Output

Formula

Description

The forward converter is an isolated DC-DC topology that transfers energy directly through the transformer during the switch on-time (unlike the flyback which stores energy). The output voltage depends on the input voltage, duty cycle, and turns ratio. It behaves like an isolated buck converter. Forward converters are widely used in the 50-500 W range for telecom power supplies, server PSUs, and industrial equipment. The maximum duty cycle is typically limited to 50% for single-switch forward converters to allow transformer core reset.

Variables

• V_out — Output voltage (V)
• V_in — Input voltage (V)
• D — Duty cycle (0 to 0.5 for single-switch)
• N₂ — Secondary winding turns
• N₁ — Primary winding turns

Practical Notes

Active-clamp or two-switch forward converters can operate at duty cycles above 50%. The output inductor and capacitor form an LC filter that smooths the pulsed transformer output into DC. For multiple outputs, additional secondary windings with their own rectifiers and LC filters are used. Cross-regulation between outputs depends on the coupling between secondary windings.