Electronic – Replace DPDT relay with Mosfet

coilmosfetpower supplyrelayups

Currently I have this UPS power setup for my Router with the help of a DPDT relay so that the router works when mains power supply fails. The working principle of my project is real simple. Two separate power supplies are connected to a DPDT relay where one the power supply powers the relay coil and a battery. When the mains power fails the relay coil is no longer powered and switches to the battery supply. I used a relay mainly because it provides full isolation between the 2 power supplies.

My concern is that in my current setup the relay coils are always powered on when the mains in available which according to Omron, might lead to a contact failure or coil burnout in the long run.

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So is there any a way to replace my relay setup with a more reliable component? maybe a Mosfet or SCR? Will the coil really get damaged?

I'm attaching the diagram of my setup
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Edit:

So I went through the below suggestions and decided to change my setup into this new one which might be better than my first one.
These are the changes that I've made.

  1. I got rid of the 9V wall wart and now it's just a single 12V 2A wall
    wart that powers everything.
  2. Now uses a CC CV Buck converter with Li-ion charging feature to charge
    batteries instead.
  3. Added a 2 Series Battery Management Module with Cell balancer feature so
    that I could now use 2×18650 cells for longer runtime and better voltage to
    boost
  4. Replaced the Boost converter with a Buck Boost converter.
  5. Scrapped the Relay.

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So, will my new setup work as intended? or is there any problem? or maybe place to improve?

Best Answer

I can't understand why you have such complexity built in to your design. Surely, this will work and is far simpler; requiring no relay and no change-over to a 9 volt supply (now redundant): -

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