Isolated high step-down DC-DC converter with current-doubler rectifier for ultracapacitor charger applications

An isolated high-efficiency, high step-down converter for ultracapacitor charger is presented. The proposed converter utilized the structure of switched inductors and combined the current-doubler synchronous rectifier, which can reduce the secondary circulating currents. In addition, the energy of the leakage inductance can be recycled to reduce the voltage stresses of the switches. Therefore, the proposed converter can supply the requirement of charging high current, and keep converting high efficiency at the same time. The maximum efficiency of the proposed converter reaches 96.53% at 350 W, and the full load 1 kW is 94.31%, in the case of input voltage 380 V and output voltage 14.6 V. Finally, a 250 F ultracapacitor is charged by the proposed converter from 0 to 14.6 V with constant current (CC) and constant voltage (CV) modes in 1 min. The proposed converters can prove their feasibility by experimental results. This paper proposed an isolated high-efficiency, high step-down converter for an ultracapacitor charger, which can charge a 250 F ultracapacitor from 0 to 14.6 V with constant current (CC) and constant voltage (CV) modes in 1 min.image