Patent ID: 6064580
Filing Date: 2000-05-16
Classification: H02M,Y02B

Abstract:
A power supply circuit comprising:first and second choke coils;first and second capacitors;first and second switching elements each comprising a MOSFET;first and second synchronous rectifying transistors each comprising a MOSFET;a transformer having a primary winding and first and second secondary windings which are magnetically coupled to said primary winding;said first and second switching elements being connected in series with each other at a junction, jointly making up a series-connected circuit, said primary winding and said first choke coil having respective terminals connected to said junction between the first and second switching elements;said first and second capacitors being connected in series with each other at a junction, jointly making up a series-connected circuit, said primary winding having another terminal connected to said junction between the first and second capacitors;said series-connected circuit of the first and second switching elements and said series-connected circuit of the first and second capacitors being connected parallel to each other, jointly making up a parallel-connected circuit; anda power supply, operably connected to a terminal of said parallel-connected circuit and another terminal of said first choke coil, for applying a voltage between said terminal of said parallel-connected circuit and said another terminal of said first choke coilwherein when said first and second switching elements are alternately tuned on, an alternating current flows through said primary winding to induce alternating-current voltages respectively across said first and second secondary windings for thereby alternately turning on said first and second synchronous rectifying transistors to cause a current to flow alternatively through said first and second secondary windings for supplying a current to said second choke coil.