| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power unit which can prevent the dielectric breakdown of a transformer due to an overload and can be downsized. SOLUTION: This switching power unit is equipped with a transformer T1, an NMOS transistor Q1 which converts DC input voltage into AC voltage by ON/OFF operation and supplies it to the primary winding L1, a translate circuit (a diode D2 and a capacitor C3) which converts the AC voltage induced in the secondary winding L2 into DC voltage prior to output, a PWM circuit 3 whose drive voltage is the voltage based on the induced voltage of auxiliary power winding L3 and PWM-controls the NMOS transistor Q1, an overload detecting circuit 4 which detects an overload, based on the induced voltage of winding L4 for overload detection, and a switching frequency changing circuit 5 which changes the switching frequency of the NMOS transistor Q1 and breaks the NMOS transistor Q1 when an overload is detected by the overload detecting circuit 4. COPYRIGHT: (C)2006,JPO&NCIPI
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