Input-Series Two-Stage DC-DC Converter with Inductor Coupling

This paper presents an input-series and inductor- coupled two-stage scheme to DC-DC converter. Discussions of the circuit in Discontinuous Conduction Mode (DCM) are provided both when inversely coupled interleaving and when directly coupled without phase shift. According to detailed analysis, inverse coupling is more beneficial for current ripple reduction when the windings are not so tightly coupled. The reason to avoid tight coupling is that current spikes and resonance due to voltage mismatch can be suppressed, since the two coupled windings have a large leakage inductance. A prototype with 500-700 V input and 5 V/30 A output is built. Experimental results verify the principle and performance of the proposed approach.