Button has played the Addicks' last three matches after Powell took the decision to drop regular number one Ben Hamer.
And the summer signing from Tottenham put in a fine display to secure a clean sheet in the 1-0 win at Huddersfield on Saturday.
Powell said: "David Button joined us in the summer and had to be really patient to earn his chance.
"I put him in last Saturday and he's played the last three games. He made some crucial saves but his handling and decision making was very good.
"I'm really pleased for him as sometimes it can be hard to keep going.
"He's had to sit by and watch Ben Hamer, who is another good goalkeeper who has done particularly well since he's joined the club.
"I'm pleased I've got two good goalkeepers and they have both shown this season that they are very capable at this level.
"But David has now got the shirt and definitely earned the clean sheet for the team."