Protection Circuit for 5V Regulator

19540Published On Nov 30,2016 11:19 AMshare0

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Generic crowbar

A generic 9.1 V, 250 mA crowbar circuit that uses a silicon controlled rectifier, or SCR, to short the output terminals

 

If the input voltage to the circuit reaches a certain threshold (9.1 V in the example above), a Zener diode breaks down and causes either a TRIAC or SCR to short power and ground... as if you threw a crowbar across the terminals.This forces a lot of current through the device but immediately lowers the voltage. An inline fuse will then electrically disconnect the load (the Wandboard in our case) from the supply. In the case of an SCR, when the Zener diode breaks down, a voltage appears on the gate terminal of the SCR. If this is above the SCR's gate activation voltage, the device turns on.

Our Crowbar Circuit

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James
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