In this letter, the series-capacitor-based boost power factor correction (PFC) converter (or called the voltage doubler PFC converter) is studied. It possesses the voltage doubler and intrinsic current balancing characteristics only when their equal duty ratios are larger than 0.5. Thus, for PFC application, the balanced-currents input voltage should be smaller than the quarter (1/4) output dc voltage. To extend the balanced-currents input voltage range, the unequal duty-ratio feedforward control is proposed in this letter. For the case of dc output voltage 400 V, the maximum input voltage with balanced inductor currents increased from 100 V (the quarter output dc voltage) to 200 V. The proposed control method is implemented in the field programmable gate array chip to evaluate its performance.