Boost Converter Duty Cycle Calculator

The boost converter\'s 1 / (1 − D) transfer function was first analyzed rigorously via state-space averaging by R.D. Middlebrook and Slobodan Ćuk at Caltech in 1976. Their paper "A General Unified Approach to Modelling Switching-Converter Power Stages" gave power-electronics engineers the first fully worked-out small-signal models for all PWM converter topologies, including the characteristic right-half-plane zero (RHPZ) that makes boost converters difficult to compensate at high bandwidth.

The practical limit D_max ≈ 0.85 emerged empirically: as duty cycle climbs past 90%, the off-time becomes too short for the inductor to fully dump energy into the output, peak currents rise exponentially, and losses from switch on-resistance and diode forward voltage dominate. Modern high-ratio boost ICs (LT3478, LT8335) implement internal duty-cycle limits around 88–92% to protect against runaway conditions.

For step-up ratios above ~7:1, designers switch topologies: flyback (uses a coupled inductor with separate primary and secondary turns ratios), SEPIC/Ćuk (handle Vin > or < Vout), charge-pump (no inductor, lower current capability), or multi-stage cascaded boosts. Each has distinct efficiency and complexity trade-offs.

Enter V_in, V_out, and expected efficiency. The tool returns the ideal duty cycle D = 1 − V_in/V_out, the real-world duty compensating for losses, the step-up ratio, and a status indicator that warns when D approaches the practical limit.

This is a quick first-pass check — a design-time go/no-go before detailed inductor and capacitor sizing. If the tool warns about D > 85%, reconsider your topology before sinking time into a boost that can\'t regulate at max load. Everything runs client-side; no values leave your browser.