Im trying to do an UPS for a new proyect with a li-ion battery like cellphones ones, it needs to be reliable as I would like to left it at home without surveillance. I have found this: answer from and old post. enter image description here

I would like to know if this works now a days, as the Post is 4 years old now, Mosfet life cycle is in "end of life" so maybe can be replaced for a new one, as far as I understand the load V is going to get determined by the drop in the Mosfet, I need 5v so maybe someone can recommend any other Mosfet with low drop?

I found this IC= BQ24079RGTR, and as far as I understand it does the same function as the circuit above?


1 Answer 1


So to cope with the voltage drop I would recommend adding a boost converter behind the MOS-FET. It will be fine if the 5V of the usb input go through it and will also improve the stability of the voltage it outputs.

For the MOS-FET you should try to get one that has pretty much the same characteristics as the one in the schematic. Most important values are the gate-source voltage Vgs and the on-resistance vs. Vgs, because if these are different the MOS-FET might not fully turn on/off.

Since I've actually taken the above mentioned circuit and improved it a little bit. You can check out the whole circuit schematic and a video about it over at instructables. Maybe you can reuse my circuit. Heres the schematic: enter image description here

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    \$\begingroup\$ I like instructables, however, now it's a linkedonly answer, so you should either elaborate about the answer/method to answer it without the link needed, or make it a comment. \$\endgroup\$ Commented Mar 1, 2018 at 14:17
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    \$\begingroup\$ If I had 50 reputation I could comment, but I think I can throw in the schematic right here. Thanks for the suggestion. I will add the schematic once I am back home. \$\endgroup\$
    – enwi
    Commented Mar 1, 2018 at 14:22

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