A Zero-Voltage-Transition Bidirectional DC/DC Converter

A three-level (TL) bidirectional dc/dc converter is a suitable choice for power electronic systems with a high-voltage dc link, as the voltage stress on the switches is half and inductor current ripple frequency is twice the converter's switching frequency. This study proposes a zero-voltage transition (ZVT) TL dc/dc converter to enable operation with higher switching frequency in order to achieve higher power density and enhance efficiency. Two identical ZVT cells, each one composed of two resonant inductors, a capacitor, and an auxiliary switch, are integrated with the conventional TL topology to enable soft switching in all four switches in both buck and boost operation modes. In addition, a variable dead-time control is proposed to increase the effective duty ratio at heavy loads. The proposed soft-switching feature has been demonstrated under different loading conditions. A 650-W prototype is designed and fabricated, which exhibits 95.5% at full load.