Stacking an auxiliary step-up circuit on top of a boost converter is one of the most attractive structures for nonisolated high step-up applications. In this paper, in order to avoid the large input current ripple of coupled-inductor-based circuits, an auxiliary step-up circuit is integrated via an additional transformer and its balancing capacitor. Avoltage-doubler is adopted as an auxiliary step-up circuit, which is inherently suitable for high-voltage applications due to its simple structure and low-voltage stress. Moreover, the transformer leakage inductor and the balancing capacitor constitute a resonant tank so that the quasi-resonant operation makes the current sinusoidal. As a result, a reduced switch turn-OFF loss and reverse recovery of the diode can be expected. The proposed converter is verified with a 24 V input, 160 W-200 V output prototype.