A 48V-to-1V Buck-Assisted Active-Clamp Forward Converter with Reduced Voltage Stress for Datacenter Applications

This paper presents a buck-assisted, active-clamp forward (ACF) converter that achieves direct 48V-to-1V DC-DC conversion for datacenter applications. To mitigate high voltage stresses on semiconductor power switches, the converter employs a buck-assisted architecture with repositioned active-clamp mechanism, which enhances system reliability effectively without adding silicon overhead. In addition, the proposed topology only requires small leakage inductance to achieve zero-voltage switching (ZVS) in the primary side stage, decreasing switching power loss greatly. In the meantime, the switching loss in the secondary side stage is inherently reduced since the current commutation speed is improved due to small leakage inductance. To validate this design, the power stages in the primary side and the secondary side are implemented using LDMOS FETs in an 0.18μm BCD process and gallium nitride (GaN) FETs, respectively. The fully-transistor based simulation results demonstrate that the proposed converter reduces the voltage stress by 25% and requires 2 times less leakage inductance for ZVS compared to conventional ACF converter.