Llc resonant converter with variable turns ratio

Abstract

An LLC resonant converter with variable turns ratio includes a switching circuit coupled to a DC input voltage for converting the DC voltage into switching signal, a resonant tank coupled to the switching circuit and configured to receive the switching signal to provide a primary current, a transformer circuit coupled to the resonant tank. The transformer circuit includes a plurality of separated transformers, each has a primary side winding and a side secondary side winding, where individual transformer has different turns of primary side winding, which can be dynamically selected to couple with the primary side winding of other transformers in series or in parallel to form a dynamically changing equivalent primary side winding, so that the turns ratio in the transformer circuit can be dynamically changed accordingly.