| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an overcurrent protective circuit for extending off-time of a switching power transistor while preventing the damage of the switching power transistor by turning off the switching power transistor without a delay even when an inrush current flows. Ž<P>SOLUTION: A transistor Q2 is turned on and a capacitor C2 for a CR circuit 14 is discharged when a detecting current by a shunt resistor Rsh1 reaches a first set value or more. A power MOS transistor Q1 is turned off by a driver circuit 11 when an output voltage reaches a set value or less. The power MOS transistor Q1 is turned on by the driver circuit 11 when a capacitor C2 for a CR circuit 14 is charged by turning off the transistor Q2 and the output voltage reaches the set value or more. The transistor Q4 is turned on and the gate voltage of the power MOS transistor Q1 is reduced and turned off when the detecting current by the shunt resistor Rsh2 reaches a second set value or more larger than the first set value. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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