Patent ID: 6252782
Filing Date: 2001-06-26
Classification: H02M,Y02B

Abstract:
A switching power supply apparatus comprising:a first series circuit connected to an input dc power supply and having a first switching means and a second switching means which alternately turn on and off with a dead time period between the turning off of one switching means and the turning on of the other switching means;a second series circuit connected to said input dc power supply and having a third switching means and a fourth switching means which alternately turn on and off with a dead time period between the turning off of one switching means and the turning on of the other switching means;a transformer having at least a primary winding and a secondary winding;a first inductor connected between a first terminal of the primary winding of said transformer and a connection point at which said first switching means and said second switching means are connected;a second inductor magnetically coupled with said first inductor and connected between a second terminal of the primary winding of said transformer and a connection point at which said third switching means and said fourth switching means are connected;wherein said first inductor is connected in series with said primary winding, and said primary winding is in turn connected in series with said second inductor;a first diode connected between the first terminal of the primary winding of said transformer and a negative terminal of said input dc power supply;a second diode connected between the second terminal of the primary winding of said transformer and a negative terminal of said input dc power supply;rectifying and smoothing means for rectifying and smoothing a voltage induced in the secondary winding of said transformer; andON/OFF control means for controlling either the duty ratio of a controllable switching device contained in said first switching means or the duty ratio of a controllable switching device contained in said third switching means, or both of said ratios.