Bryan Ruiz found the net twice for the home side, who slipped to 12th place.
Hull City secured a place in the Premier League for next season earlier on Saturday after drawing 2-2 at home to already-promoted Cardiff City on the final day of the Championship season.
Watford, Brighton and Hove Albion, Crystal Palace and Leicester City will contest the play-offs.
Wolverhampton Wanderers were relegated following their defeat at Brighton.
Additional reporting by staff writer