I would like to protect a load against overvoltage by cutting one of its power lines when the voltage exceeds a set value.
All the examples I have seen online present a way to short circuit the supply but not open it. I can't short circuit the supply nor use a Zener for regulation as the current drawn would be too high (and would limit it under normal conditions).
- How can I drive a series transistor to cut one of the lines when a control voltage (from a comparator) is driven high (or low)?
- How can I make sure that this protection is unengaged (i.e. supply is on) when the protection unpowered?
- How can I make sure it can automatically disengage itself when the voltage goes back within allowed range?
In my case, an alternator generates a voltage which is rectified and fed in a big capacitor before supplying a voltage regulator. I am designing the circuit for a certain alternator rate, but I want to protect it in case it goes faster. 2) comes from the fact that the protection circuit will be powered by the regulator past it... Which means, if it's engaged when unpowered the entire system will never power on!