Shortcircuit protected voltage regulator


Posted on Mar 25, 2013

At this voltage regulator prototype the maximum current, with output shortcircuited it was only 0,5 A, so no overheating occured. In this dc voltage regulator circuit, T1 is for current limitation. As soon as the voltage on the R2+R3 becomes higher than 0,6-0,7 V, T1 opens, which leads to a reduction to zero of the T2 base current. The voltage at which the shortcircuit protection starts to act, is given by voltage sum on R2 and R3. R3 and R4 resistances form a T2 voltage divider.


Shortcircuit protected voltage regulator
Click here to download the full size of the above Circuit.

Voltage regulator IC’s, with 3 pins, from LM7805 and LM7812 series are excellent for usage in voltage regulator circuits. If you need higher currents, up to 3 A, you must add a complementary transistor, T2 in this schematic. In a normal design, in case of a shortcircuit, the power dissipation can be very high. This problem can be solved using the voltage regulator design presented bellow.




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