LAUSR

This article presents a three-switch zero-voltage switching (ZVS) step-up/-down hybrid dc–dc converter with e-mode GaN transistors for wide-input-range applications. With a flying capacitor, the proposed hybrid converter saves one auxiliary branch for establishing ZVS and one power FET compared with the conventional buck–boost counterpart, thereby reducing the converter volume and power loss. The capability of having ZVS turn-ON of all power FETs enables the proposed converter to operate in the MHz range under high input voltages by removing the switching power loss. The flying capacitor in the proposed converter further lowers the main inductor current in the step-down mode, significantly decreasing the conduction loss of the inductor. The proposed converter was validated using three 100-V e-mode GaN HEMTs with the on-chip gate drivers implemented in a high-voltage 0.5- $\mu \text{m}$ process. The proposed converter supports a wide input range from 9 to 45 V with a maximum 48-W output power, operates at 2 MHz, and achieves peak power efficiencies of 97.6% and 96% in step-down and -up modes, respectively. The volume of the external components in the proposed converter is also reduced by at least three times compared with the prior art.