| 摘要 |
<p>A switching power supply in which the synchronous rectification switch of a synchronous rectification circuit can be turned on only for a desired time. The switching power supply comprises a main switch (Q1) connected with a DC power supply (1) through a primary winding (N1). The secondary winding (N2) is connected with a smoothing capacitor (Co) through a synchronous rectification element (Q2). The synchronous rectification element (Q2) comprises a parallel circuit of a synchronous rectification switch (8) and a diode (Do). In order to turn on the synchronous rectification switch (8) during a period where the diode (Do) is turned on, a capacitor (C1), first and second current sources (9,10), a conductible period detecting means (13), and a comparison/pulse formation circuit (14) are provided.</p> |
