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| Switch between power sources automatically |
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| OM222O:
Hello I have a project that runs on a battery and a 12v jack. I can detect the voltage at 12v line and switch to it when I detect a voltage. there is also a capacitor that allows the MCU to operate and switch back to the battery when the 12v line is disconnected. my only issue is coming up with a way of actually doing that ... I initially tried using mosfets but then the 12v line back feeds the battery via the body diode of the fet which is no good ... a mechanical solution such as a relay is also no acceptable. I also can't really use diodes as the device can pull up to 5 amps and that's simply way too much of wasted energy and heat do deal with. are there any easy solutions that come to mind for switching between the two sources? thanks! |
| KC0PPH:
Use a Diode if current is not too much. 12V Supply goes directly to your circuit 12V Battery goes through a diode. If you want protection against backfeeding your 12V supply use 1 diode in series with your 12V supply and 2 in series with your battery. Quick and dirty and works like a charm. |
| SiliconWizard:
One way of avoiding to be bothered with the body diode is to put two MOSFETS back-to-back. |
| OM222O:
I'm sorry if this sounds stupid but I'm not sure how back to back fets would work. Can you please provide a schematic? |
| madires:
Search for "ideal diode" or "power oring". For example LTC4359 which I'm using for one of my projects. |
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