| 摘要 |
PROBLEM TO BE SOLVED: To provide an overcurrent protection circuit and a DC power supply device which is hardly affected by the fluctuation of a process or device, wherein the drop of an input voltage and an output voltage can be reduced, and the maximum current value and a short-circuit current value can be set. SOLUTION: In a normal operation mode, an operating amplifier A1 and an output transistor P5 are operated, and an output voltage is constantly maintained. In a current restriction mode when large currents are poured from an input terminal IN according to a transient reply, a transistor P4 is controlled by a transistor P3 and an operating amplifier A3, and the maximum currents flowing to the output transistor P5 are controlled so as to be constantly held. In a fold back mode when the voltage drops, a transistor P2 is controlled by a transistor P1 and an operating amplifier A2, and short-circuit currents flowing to the output transistor P5 are controlled. In this case, the operator A2 reduces the output currents according to the output voltage by using a current source gm for constantly holding mutual conductance. COPYRIGHT: (C)2006,JPO&NCIPI
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