Patent ID: 6972656
Filing Date: 2005-12-06
Classification: H02M

Abstract:
1. A switching power supply device comprising: a transformer having at least a first primary coil, a first secondary coil, a second secondary coil and a second primary coil, which are laminated in the sequence of said first primary coil, said first secondary coil, said second secondary coil that is adjacent to said first secondary coil, and said second primary coil, and having a configuration wherein a center tap is drawn out from a connecting part between one end of said first secondary coil and one end of said second secondary coil; a switching part for alternately applying a voltage in a forward direction and an inverse direction to said transformer; a rectifying part for rectifying the voltage induced across said center tap of said transformer and the other end of said first secondary coil or the other end of said second secondary coil; a smoothing part for smoothing the voltage of said rectifying part; and a control part for controlling the on-off of said switching part so that said first primary coil and said second primary coil are opened when said switching part turns off, then the magnetic fields induced by a current flowing in said first secondary coil and a current flowing in said second secondary coil cancel out each other by flowing currents in inverse directions to each other in said first secondary coil and said second secondary coil, so as to maintain the continuity of the magnetic flux of said transformer.