Coventry City supporters will be going to MK Dons next season after Karl Robinson's side won at Huddersfield Town but failed to over-turn a 2-0 first leg deficit.
Jordan Rhodes put Huddersfield ahead in the 18th minute only for Powell to level on the night in the 39th minute.
In the third minute of second half stoppage time, Smith hit a winner for MK Dons but it was not enough to stop Huddersfield Town from booking their place in the League One Play-Off Final against Sheffield United on May 26th at Wembley.