| 摘要 |
PURPOSE: A power supply apparatus is provided to control the electric potential of a base resistance and to prevent the base resistance by returning terminal voltage of a reference resistance to a transistor, a partial pressure resistance and a current mirror circuit. CONSTITUTION: A current detecting resistance is integrated with a power transistor(TR) and serially connected to a through line between an input terminal(P1) and an output terminal(P2). Terminal voltage of a current detecting resistance is fed to an over current protection circuit(14) from input terminals(P13,P14) of a control IC(12). In the over current protection circuit, the terminal voltage is compared with reference voltage(Vref2) obtained from a reference voltage source(19) in an error amplifier(18). Also, the error amplifier prevents a base current by communicating a control transistor(Q10) arranged between the base of the control transistor and a ground terminal(P15) and bypassing a control current if the terminal voltage is higher than the reference voltage.
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