| 摘要 |
PURPOSE:To prevent the malfunction of a protecting circuit by providing a protecting circuit for releasing the output when the output voltage decreases and a controlling circuit for resetting a reference voltage setting circuit to the initial state in response to the closure of a power switch. CONSTITUTION:A switching power transistor 2 provided between a DC power source 6 and a load 26 compares the output voltage with the reference voltage of a setting circuit 32 and controls through a transistor 10. A protecting circuit which has a reference voltage setting circuit 42 for setting another reference voltage, a comparator 44 and a capacitor 58 is provided, serves to turn off the transistor 2 when the output voltage is abnormally decreased, and a reference voltage setting controlling circuit 64 is provided to rapidly discharge the remaining charge of the capacitor 58 at the initial time upon closure of the power source. Accordingly, it can completely prevent the malfunction of the protecting circuit 40 when closing or opening the continuously operating power source and can improve the safety. |
