Patent ID: 6201713
Filing Date: 2001-03-13
Classification: H02M

Abstract:
A switching power supply unit for providing a DC output comprising:a DC power supply;a transformer having a primary winding and a secondary winding;a main-switching element for connecting in series to the primary winding for performing ON/OFF operations;at least one sub-switching element for performing ON/OFF operations at least one of in synchronism with and in opposition to the ON/OFF operations of the main-switching element, the at least one sub-switching element having main switched terminals provided in a power line coupled to a load connected to the switching power supply unit, power to or from the load passing through the main switched terminals;the transformer having a sub-switching-element drive winding for generating a voltage turning the at least one sub-switching element on;a turn-off switching element turning the sub-switching element off; anda time-constant circuit for controlling the turn-off switching element.