Novel Active Clamping Step-Down DC-DC Converter with Lower Voltage Stress

In this paper, a novel ZVS buck converter with lower voltage stress based on coupled-inductor and active clamp techniques has been proposed. This converter utilizes coupled-inductor to obtain higher step-down ratio than the conventional buck converter. Moreover, the proposed converter can achieve ZVS (Zero-voltage switching) on both switches from full load to extra-light load. Therefore, the efficiency at light load does not subject to the switching losses, which leads to higher overall efficiency. The ZVS conditions and the design considerations of proposed converter are described. The ZVS region can cover the full load range, if the value of the magnetic inductance and resonant inductance have been properly chosen. Finally, based on controller TMS320F28035, a converter with 156 V input voltage, 48 V output voltage, and 200 W output power is developed to prove the feasibility of the proposed converter. The highest efficiency is around 96.8% when operating at 125 W.