| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a power supply unit with an inrush current prevention function, capable of always ensuring proper start regardless of a load state. Ž<P>SOLUTION: A switching power supply unit 10 is provided with a resistor 16 for inrush current limit to prevent an inflow of inrush current during starting. When a voltage V4 across an electrolytic capacitor 82 in a working drive power circuit 62 is a predetermined value Vr or more after starting, a switch 20a of a relay 20 is turned on. However, when a load with a large capacity is under such a state as to be connected to an output terminal 54 in starting, a large current passes through a load from the output terminal 54 and a large voltage drop occurs through the resistor 16 for inrush current limit, so that a monitor voltage V4 may not reach the predetermined value Vr or more. To solve such a disadvantage, a no-load state is forcibly generated during starting. A mute control circuit 88 is one of components for the purpose. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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