The 22-year-old dynamo said Welton was "the only club that I want to play for" and revealed he was "proud" he was extending his stay until 2012.
The former Cherry star told WeltonTV: "First of all I am really proud that the club has offered me a four-year contract.
"I've been here for a season now and I have to say that I've loved every minute of it.
"I'd like to think that I have immersed myself into the club culture.
"It's something I had to do after being at one club for about 16 years but it was easy for me to do because from day one this club sucks you in.
"From the outside looking in you don't know what to expect but I found when I came here that the spirit and the togetherness of the club is fantastic."
Coupland said the new deal was tied up very quickly.
"Loyalty is a big thing in my life and this is the only club that I want to play for. It's a great club and I want to finish my career here," he added.