LM317T application circuit

Published:2011/5/13 4:17:00 Author:Nicole | From:SeekIC

LM317T can be used to make adjustable regulated power supply, the load is often damaged due to the potentiometer's poor contact lead to voltage rise. If a triode is added(As shown in the figure), under normal circumstances, T1's base level is 0, T1 cuts off, it has no influence on circuit; when the W1 is poor contact, T1's base level rises, when it rises to 0.7V, T1 turns on, LM317T's adjustment terminal voltage drops, output voltage drops too, it can protect the load. If the triode is removed and the W1 middle point connecting line is cut off, 3.8V bulb will be burned down immediately, the output voltage reaches 21V. If it is added T1, the brightness of bulb will reduce, then LM317T output voltage is only 2V, it can effectively protect the load.



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