Why does my charging gets disconnected itself and it repeats everytime

Hi Manish,

You'll want to eliminate all the possible sources of the problem outside of the phone first and if none of those are what's wrong then start looking at the inside of the phone.

Start with the power outlet and make sure it works by plugging a lamp into it or trying a different socket.

Next, make sure your charger is actually putting out power by either trying a different one or using it to charge a different device. Same with the charging cord; either swap it out or plug it into something else to make sure you're getting power out of the cord.

Once you've checked all of those things you'll want to look at the charging port itself. Get a magnifying glass and a bright light and look inside the port. Check for bent or broken pins and any dirt, dust or lint that's lodged inside the port. Clean it out with a toothpick, microfiber eyeglass cloth and some 90% or higher isopropyl (rubbing) alcohol.

Now try charging it again. If it's still doing the same thing, chances are you probably need to replace the charging port. The good news is it's relatively easy to do on your phone and doesn't require any soldering skills. Sorry to say iFixit doesn't have a guide for replacing the auxiliary board that holds the charging port, but there's a Spanish site called Nadie Me Llama Gallina that has just what you need.

Manuales / Xiaomi Redmi Note 9 Pro / Auxiliary board

You shouldn't have any problem finding a replacement board; I usually start with Amazon, eBay and AliExpress depending on your delivery time vs. cost considerations.