Wigan took control of the match in the early stages at the DW Stadium and the hosts could have been ahead in the eighth minute when Powell's chipped effort was pushed wide by Jasmin Handanovic.
Maribor started to enjoy more of the possession as the first half progressed but the visitors were dealt a blow when they fell behind in the 22nd minute.
Handanovic failed to punch clear a cross from Jean Beausejour and Powell took full advantage by heading the ball into an empty net.
Wigan grew in confidence following the breakthrough and continued to dominate possession before finding their second goal.
Beausejour was involved once again as he delivered an inviting cross for Ben Watson to convert from close range.
Powell could have scored his second goal shortly before the break but he clipped the ball over the crossbar after sprinting beyond the Maribor defence.