| 摘要 |
PROBLEM TO BE SOLVED: To provide a step-up type switching power supply unit reducing rush current into an output capacitor when activated. SOLUTION: This step-up type switching power supply unit has a current limit transistor M5 having an ON resistance voltage larger than that of a synchronous rectification transistor M1 between an external terminal T1 and an external terminal T2. In the power supply unit, when shifting from a standby state to an active state, a control section 1 turns on the current limit transistor M5 only for a predetermined period before starting switching control of the synchronous rectification transistor M1. COPYRIGHT: (C)2010,JPO&INPIT |
