A Novel Quadratic High Step–Up DC–DC Converter with ZCS Based on Expandable Coupled Inductor with Switched Capacitor Cell

Conventional quadratic boost DC–DC converters can achieve high voltage gain; however, the main switch is subjected to voltage stress approaching the output voltage. Some improved topologies also suffer from limitations such as the absence of a common ground, discontinuous input current, or increased control complexity arising from multiple switches. To address these limitations, this paper proposes a single-switch quadratic high step-up DC–DC converter that integrates a coupled inductor with expandable coupled-inductor switched-capacitor (CLSC) cells. By adjusting the turns ratio of the coupled inductor and the number of CLSC stages, the proposed converter achieves high voltage gain at a relatively low duty cycle while providing a common-ground configuration, continuous low-ripple input current, and reduced voltage stress on the main switch. An integrated passive clamp circuit recycles leakage-inductance energy and suppresses voltage spikes across the main switch, while several diodes operate under zero-current switching (ZCS). The operating modes, steady-state characteristics, component stresses, and design guidelines are comprehensively analyzed. A 200 W prototype operating at 50 kHz with an input voltage of 20 V and an output voltage of 320 V was developed for verification. At an output power of 120 W, the measured voltage stress on the main switch was 125 V, substantially lower than the 320 V output voltage. Over an output power range of 30–200 W, the prototype achieved a peak efficiency of 94.96% at 50 W, while the deviations between the simulated and experimental voltage values remained within ±1%. These results verify the feasibility and high step-up performance of the proposed converter and demonstrate its potential for renewable-energy and high-voltage conversion systems.