0
\$\begingroup\$

I have a circuit which works with a battery normally. The nominal voltage of battery is 3.7 V and I am using boost converter to make it 5 V. And I have a charging circuit of this battery too. So, my aim is when the USB cable plugged, I want to boost circuit stop working. So, it is like a switch controlled by a 5 V. Like normally closed relay.

How can I do this? I tried MOSFET and BJT transistors at the input port of the boost circuit but these are caused voltage drop.

As a result, how can I disconnect 3.7 V from boost circuit when 5 V is plugged?

Boost circuit: enter image description here

Charging Circuit:

enter image description here

USB input:

enter image description here

\$\endgroup\$
4
  • 1
    \$\begingroup\$ Are you dead set on using the 34063 or could you consider a (modern) DC/DC with EN-pin? That would make the task much simpler. Also probably more efficient... \$\endgroup\$
    – winny
    Commented Oct 9, 2020 at 11:41
  • 1
    \$\begingroup\$ Read the application note on Adding shutdown feature to MC33063A, MC34063A switching regulators \$\endgroup\$
    – Finbarr
    Commented Oct 9, 2020 at 11:47
  • \$\begingroup\$ Why don't you make your boost circuit provide 4.9 volts and just connect the 5 volts from USB directly to Vcc. The action of raising Vcc by 0.1 volts should cause the boost circuit to shut-down into fairly low power (if that is enough for you?). \$\endgroup\$
    – Andy aka
    Commented Oct 9, 2020 at 12:02
  • \$\begingroup\$ @Finbarr Yes in the file that you shared there is a load switch to do that, How can I simulate this ic? I can not find the LTSpice symbol of it. Can I simulate it on altium? I am new in altium \$\endgroup\$
    – ratatosk
    Commented Oct 10, 2020 at 8:44

1 Answer 1

Reset to default
0
\$\begingroup\$

I figured it out with adding diodes and selected another regulator which has enable pin. The circuit is below.

enter image description here

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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