Optimized active-clamp circuit design for an isolated full-bridge current-fed DC-DC converter

This paper presents a new method for the capacitance selection of an active-clamp circuit to enhance the performance of an isolated current-fed full-bridge DC-DC converter. The developed approach can reduce the circulating energy through the bridge switches using an appropriate choice of the resonant frequency between the transformer leakage inductance and the clamp capacitance in relation to the switching frequency. Thus, current and the voltage stresses can be reduced and the converter efficiency improved. It has also been demonstrated that the use of a voltage-doubling output rectifier enhances the performance further. The optimized active-clamp circuit has been implemented on a 1.2 kW isolated current-fed full-bridge DC-DC converter and test results have confirmed the claimed improvements.