| 摘要 |
PROBLEM TO BE SOLVED: To provide a power supply circuit for quickly charging output capacitor, and for achieving low dark currents at battery connection and the like, and for achieving overheat protection at output short-circuiting. SOLUTION: When a power supply circuit is connected to a battery 5, a P-channel MOSFET(M1) of a timer conduction circuit 4 is turned on, and the output voltage of the battery 5 is supplied via a clamp circuit 3 to a series regulator 1, and the terminal voltage of an output capacitor 2 is increased. When the inter-gate/source voltage potential difference becomes smaller than the threshold voltage due to the charging characteristics of a resistance R1 and a capacitor C1, the M1 is turned off. As a result, while the M1 is turned on, the charging of the output capacitor 2 is completed. Thus, even if the output is short-circuited, after the M1 has been turned off, currents will hardly flow; and since only small currents determined by the resistance R2 will flow, the the clamp circuit 3 can be prevented from exceeding the allowable loss. COPYRIGHT: (C)2007,JPO&INPIT
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