Electronic – the simplest way to turn off some circuit when supply voltage reaches a minimum level


Knowing I have only a 12V battery to supply my circuit, how I can turn off the circuit if the voltage reaches 11V? I cannot use simple comparator CI since I don't have another supply voltage. I could I do that?

Best Answer

Get a comparator that runs from (say) 10 volts and, feed power to it via a low drop-out regulator. The LDO regulator is 10V and this can be potted down to (say) 5V (easy). This is your measurement reference input.

This reference feeds one input of your comparator. The other input is fed from your battery via another potential divider. Set this 2nd potential divider to produce 5V when the battery is 11 volts.

The output of the comparator will switch as the battery falls below 11 volts and this switching output can drive a relay to disconnect your load.

You could also use a mosfet instead of the relay.