Forward Converter Calculator

A forward converter is an isolated DC-DC topology that transfers energy from a transformer primary to its secondary while the main switch is on. Unlike a flyback converter, it does not intentionally store the full cycle energy in the transformer core. The output rectifier and inductor smooth the secondary pulses into a regulated DC output. This calculator estimates the ideal duty cycle from input voltage, desired output voltage, and the entered primary-to-secondary turns ratio. It also calculates output power, required input power, average input current, and switching period. The voltage relationship used here is output voltage equals duty cycle multiplied by input voltage divided by the turns ratio. Rearranging gives duty cycle equals output voltage multiplied by turns ratio divided by input voltage. The turns ratio must therefore be entered consistently as primary turns divided by secondary turns. A calculated duty cycle above 100 percent cannot be produced, and practical single-switch forward converters normally need substantially more reset margin. Semiconductor voltage drops, winding resistance, leakage inductance, dead time, and control limits further reduce the available output voltage. Output power is output voltage multiplied by output current. Estimated input power divides that value by the decimal efficiency, so an efficiency of 0.85 means 85 percent. Average input current then equals input power divided by input voltage. These are steady-state averages useful for an early power-stage estimate, not peak switch or winding currents. Peak values depend on magnetizing current, output-inductor ripple, transformer design, switching transitions, and the chosen current-conduction mode. The switching period is one divided by frequency and is displayed in microseconds. Use the result as a first design check before selecting a controller, transformer, reset network, rectifiers, and output filter. Verify that duty cycle stays within the controller and core-reset limits over the full input range. Choose components for worst-case voltage, current, temperature, and transient stress rather than nominal averages alone. Real efficiency changes with load and operating frequency, so measured loss data or a detailed loss model should replace the single efficiency estimate in a production design. Isolation spacing, thermal design, electromagnetic compatibility, control-loop stability, and fault protection also require separate engineering analysis.