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Electric crowbars protection circuit

2016-09-11 19:58  
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 One way to protect a circuit from over-voltages is to use a "crowbar circuit". The idea is to short the power supply rail to ground if an over-voltage is detected and thereby quickly forcing it down to a harmlessly low voltage and blow a fuse or trigger some other over-current protection mechanism. The name of the circuit probably comes from the analogy of throwing a crowbar (or some other thick metal object) across the supply rails to short them.Crowbar protection circuit is used where we need protection against high voltage surge.Electric crowbarsprotect the electrical components of these generators. An electric crowbar is a circuit that intentionally shorts out.To avoid grief when using 12-V power supplies with mobile transceivers, especially when there is a short -circuit failure of the series pass transistor, crowbar circuits provide protection by clamping the power line and blowing the fuse within microseconds of an overvoltage condition. It is a good idea to incorporate the crowbar directly into the transceiver.The main difference between the two circuits is that less complex circuit B depends on component tolerances for the exact trigger level, while the circuit A includes a unijunction trigger to permit precise setting of the operating point.A crowbar circuit is an electrical circuit used to prevent an overvoltage condition of a power supply unit from damaging the circuits attached to the power supply. It operates by putting a short circuit or low resistance path across the voltage source, much as if one dropped a tool of the same name across the output terminals of the power supply.
 

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