An example of LM317T application circuit

Published:2011/8/10 4:03:00 Author:Nicole | Keyword: application circuit | From:SeekIC

The load of this adjustable regulated power supply which is produced by LM317T is always damaged due to the output voltage rises which is caused by potentiometer's poor contact. If adding a triode(as shown in the figure) under normal circumstances, T1's base level is 0, T1 turns off, it has no influence on circuit; when the W1 is poor contact, T1's base current rises, when it rises to 0.7V, T1 turns on, it makes the regulation terminal voltage of LM317T drop, the output voltage drops too, then to protect the load. If it removes the triode, and cuts W1 connection conter point, 3.8V bulb is burned down immediately, the output voltage reaches 21V. When it is added T1, the brightness of bulb reduces, then the LM317T output voltage is only 2V, it can effectively protect load.



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