| 摘要 |
PURPOSE:To lower an electric current limiting value when a load is short-circuited by connecting the base, collector, and emitter of a current limit detecting transistor to an output voltage regulating terminal, error amplifier circuit, and the base of a controlling transistor, respectively. CONSTITUTION:The base, collector, and emitter of a current limit detecting transistor (TR)22 are connected to an output voltage regulating terminal 20, emitters of TRs 8 and 9 of an error amplifier circuit 11, and the emitter of a controlling TR13, respectively. Since the electric potential of the terminal 20 drops to a level almost equal to the earthing potential when a load 21 is short-circuited, the base potential of the TR also drops. Therefore, the TR22 is turned on and a collector current flows to the emitter resistance 10 of the circuit 11, then, the emitter potential of the TR8 is raised and the electric current is narrowed down. Consequently, the limiting current when the load is short-circuited is suppressed to about 1/2 of the maximum current limiting value of the TR13 and the controlling TRs 3 and 13 are protected. |
