| 摘要 |
PURPOSE:To avoid the generation of heat of a power supply by connecting a 3rd transistor which is started by a charging current of a capacitor and cut off with drop of the output voltage between the 1st and 2nd transistors. CONSTITUTION:In an overcurrent state a transistor (TR) 4 is driven by the voltage drop of an overcurrent detecting resistance 2 and a TR 5 on a line is insufficiently driven to cause the drop of the output voltage. When the output voltage drops lower than the voltage level of a constant voltage diode 18, a TR 16 is not driven any more and cut off. Accordingly, the TR 5 is also cut off so that the generation of heat can be avoided in an abnormal state (overcurrent, short circuit, etc.). The similar actions and voltage drop to those said above are produced also in case where a control circuit 8 drives a TR 7 at a starting time point by an ON/OFF signal (signal input terminal 11).
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