Resonant switching power source having first and second switching elements connected in series to a dc power source

Abstract

The transformerused for the present invention, comprises a core of E-shaped first and second core halvescoupled together in opposed relation to each other to form a closed magnetic circuit or circuits for supporting primary and secondary windingswound around first and second core halves; and a gapdefined between end surfacesof first and second core halvesby spaced relation of end surfacesto also form a reduced section areaby contacting the end surfaces. When a large amount of electric current flows through resonant series circuit, reduced section areacomes to magnetic saturation to reduce an excitation inductanceof transformer, more increase excitation current Iand thereby perform steady operation in any load condition. When a small amount of electric current flows through resonant series circuit, excitation inductanceof transformeris increased to repress excitation current I, thereby reducing power loss during light or no load to improve power conversion efficiency during light load.