Retrive data from Broken + Locked Screen Samsung Galaxy S Duos
The problem is not with the phone, but with the charger!

I've experienced this as well with cheap crapware (possibly Chinese-made). The reason they cause this behavior is the cheap design that doesn't provide a sufficient decoupling of the voltage and also a bad ripple current.

Furthermore, they do not meet any safety standards. The one I used blew the fuse of my house. Thankfully, no other devices damaged. Also, a Chinese woman has reportedly been electrocuted by using a cheap charger.  Whether it's true or not, I strongly advise against using those chargers. It doesn't have to be from the phone manufacturer, but it's for sure a good idea to get some quality (and none-fake!) charger.

Once you use the original charger again, your phone should be working again normally.

PS:
Read this article for an in-depth explanation at the example of fake iPhone-chargers
http://www.righto.com/2012/03/inside-cheap-phone-charger-and-why-you.html