Llc series resonant dc-to-dc converter

Abstract

The present invention discloses a DC-to-DC converter. The DC-to-DC converter includes a square wave generator for generating a sequence of output voltages having a waveform of square wave. The DC-to-DC converter further includes a resonant tank connected to the square wave generator comprising a series capacitor connected to a series inductor and a parallel inductor. The DC-to-DC converter further includes a transformer having a primary side connected in series with the series inductor and connected in parallel to the parallel inductor. The transformer further includes a secondary side for connecting to a rectifying circuit for providing a rectified DC voltage to an output load circuit. The series capacitor functioning with the series inductor to provide a first characteristic resonant frequency represented by ƒ , and the series capacitor functioning with the series inductor and the parallel inductor to provide a second characteristic resonant frequency represented by ƒ wherein ƒ >ƒ . The converter runs at variable frequency switching to perform output regulation. The converter features high conversion efficiency at high input operation by switching at frequency between the first and second characteristic resonant frequency. In a preferred embodiment, the parallel inductor is integrated to transformer as primary magnetizing inductor and in further the series inductor may also be integrated into transformer.