Patent ID: 6130824
Filing Date: 2000-10-10
Classification: H02M

Abstract:
A switching power supply unit for providing a DC output comprising:a DC power supply;a transformer having a primary winding;a main switching element performing ON/OFF operations and connected in series with the primary winding; andan auxiliary switching element for performing ON/OFF operations in synchronism with or opposite to the ON/OFF operations performed by the main switching element the auxiliary switching element having an ON time;the transformer having an auxiliary switching element drive winding;wherein the auxiliary switching element drive winding generates a voltage turning on and off the auxiliary switching element; and further comprising:a first impedance circuit including a first resistor, a first capacitor being connected in series with the first impedance circuit, and a differentiating circuit for determining a timing for turning on the auxiliary switching element and the ON time thereof and being connected to the auxiliary switching element drive winding.