0
\$\begingroup\$

I have a circuit that draw 150 ma and i use 6V/4Ah dry cell to supply. Voltage regulator of this circuit needs minimum 8V so I use boost converter to draw the battery voltage to 8 volts.This converter works up to 2 volt.

enter image description here I would like to stop this module when battery goes below 4-5 volt. I tried this circuit with converter. enter image description here

It worked but when i connect the converter to system the input voltage of the converter is decrease and converter is not work even battery at 6V. I would like to learn why this circuit not worked and what can i do to work this circuit for cut off the voltage under 4-5 volt.

\$\endgroup\$
4
  • 1
    \$\begingroup\$ Where exactly is your second circuit connected to the first? Where is the input and the output? \$\endgroup\$
    – Aaron
    Nov 6 '19 at 16:46
  • 1
    \$\begingroup\$ You should also tell us why you think the second circuit should cut off the voltage under 4-5 volt. (The second circuit makes no sense to me) \$\endgroup\$ Nov 6 '19 at 17:20
  • \$\begingroup\$ @Aaron second circuit is connected to input of the input of the converter. (IN+) \$\endgroup\$
    – 7navy4
    Nov 6 '19 at 17:43
  • \$\begingroup\$ @StefanWyss when voltage level goes under to 2V converter stop the convert. I thought if i drop the input of the converter to 2v converter stop work so add that circuit between battery and boost converter but my thought is failed. \$\endgroup\$
    – 7navy4
    Nov 6 '19 at 17:49
1
\$\begingroup\$

The usual way of doing this is to use a comparator circuit that compares a reference voltage with the battery supply voltage. If the battery supply voltage falls below the reference voltage, the comparator disconnects the load e.g. with a P-channel FET.

As for the reference, you can use a simple zener diode (which is not a good reference) or better a voltage reference (e.g. TL431). Because the comparator also needs to be powered with the battery (down to 5V), you need to use a much lower reference than 5V. So you could e.g. take a 2.5V reference and compare that with the comparator against a voltage divider with 1:1 resistor ratio from the battery.

\$\endgroup\$
3
  • \$\begingroup\$ Can i obtain 5v for reference from battery with voltage divider or another method? \$\endgroup\$
    – 7navy4
    Nov 6 '19 at 17:52
  • \$\begingroup\$ I added some thoughts on the reference \$\endgroup\$ Nov 7 '19 at 17:16
  • \$\begingroup\$ A TL431 is a nice cheap configurable voltage reference. Might not be a bad idea to mention it in this answer. \$\endgroup\$
    – Hearth
    Nov 8 '19 at 18:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.