Zero-voltage transition soft-switching step-up Cuk power factor converter circuit

In conventional Cuk power factor correction (PFC) circuits, the switching devices experience high voltage and current ripples, leading to switching losses and poor power transfer capability. To address these challenges associated with conventional boost circuits, we proposed a zero-voltage transition (ZVT) soft-switching step-up Cuk PFC converter. This circuit reduces input and output ripples while minimizing switching losses, enabling the switching devices to achieve a unity PFC with zero-voltage switching operation. The proposed ZVT network facilitates zero-voltage turn-on and turn-off for the primary switching device, while allowing the auxiliary switch to achieve zero-current turn-on. Additionally, it ensure that the diodes naturally turn off under zero-current conditions, thereby reducing reverse recovery losses and enhancing converter efficiency. Once the auxiliary switching device is turned off, the resonant inductor within the proposed topology resets, irrespective of the state of the main switching device, enabling operation across a broad range of duty cycles. Furthermore, we established an equivalent circuit model to elucidate the soft-switching operation, providing a comprehensive analysis of the operating principles and processes. We derived the device stresses and conditions required for soft switching and investigated key design parameters. To validate the effectiveness and feasibility of the proposed circuit, we developed an experimental prototype operating at a switching frequency of 100 kHz, delivering an output of 400 V / 0.75 A. The ZVT soft-switching scheme enhanced the efficiency of the step-up Cuk PFC converter, with a peak efficiency of 98.35%. The proposed converter achieved high-efficiency power conversion.