It was Connecticut's third straight victory.
The Lynx closed to within 74-69 on Sheri Sam's three-point play with 2:09 remaining, but the Sun put away the contest by scoring the next 10 points. Johnson, who finished with 20 points, was six for six from the foul line during the spurt.
McWilliams-Franklin and Nykesha Sales each chipped in 17 points for Connecticut, which was 22 of 26 from the line.
Katie Smith led Minnesota with 20 points, but was only seven of 16 from the field. Sam contributed 17 points for the Lynx, while Jordan Adams recorded a double-double off the bench with 13 and 10 rebounds.