Goalkeeper Ben Alnwick had already made three outstanding saves when Smith headed the only goal of the game in the fifth minute.
Rhoys Wiggins came closest to equalising for Charlton but his 30th-minute shot was palmed on to the post by Ipswich goalkeeper Dean Gerken.
With just two wins and seven goals at home this season, Powell knows where the problem lies.
"We haven't scored enough, that is in black and white," he said.
"We don't concede too many for a side in the bottom half but goals win games.
"You need to score, even if you just nick one that can be enough.
"You have to take the chances that come your way, then it gives you something to build on or hang on to.
"I knew they would start fast and we told the players they would. That's what has won them the game.
"In the Championship, invariably teams who get ahead take a point or three. We had warnings in those first five minutes and we could not see it through. Then it was us chasing the game.
"They defended deep and manfully. They scored from a set play then they defend for 86 minutes and go home with the win.
"I won't use playing Tuesday against Doncaster as an excuse, the players are fit enough to play Tuesday, Saturday, Tuesday."
After Wiggins' tackle denied David McGoldrick, Alnwick brilliantly saved Smith's header to concede a corner from which he produced a double save that denied Darryl Murphy and Christophe Berra.
However, he was beaten from another corner when Smith headed home and from then on Ipswich held on comfortably.
Town manager Mick McCarthy said: "We've played better than that away and lost games.
"The three points is the biggest plus, then winning away and then the clean sheet.
"I wanted to approach it with a real fast start, we could have been 2-0 up in the first few minutes.
"And then we've had a good defensive performance and kept a clean sheet.
"Tommy and Christophe had to put in real battling performances as their front two were a handful. Simon Church looks like he has found his mojo again.
"I thought we handled Cameron Stewart well and Aaron Cresswell was great in his first game back.
"This league will be tight until the end. Look at Doncaster losing to Charlton in midweek and then beating QPR today.
"It will be 50-odd points to stay up again and anyone of us can beat anyone else and that is what makes it such a tough evil league to play in."