It was an emotional night for Powell, having been handed his first coaching role by Foxes boss Nigel Pearson.
In the 2-1 win, Yann Kermorgant was another person to return to haunt his previous employers - scoring the first then setting up Danny Haynes for a stunning 20-yard winner after Chris Wood had equalised for the hosts.
Powell said: "I've done the double over Leicester and my mentor and I don't know how to feel really. I'm pleased for my club and pleased for my group of players. We needed a result and they were made to work hard for it.
"It's huge because we had lost three games and drawn one in our last four. We've been playing well but we've just been getting hurt by late goals and a poor goal conceded at Hull on Saturday. It's fallen for us this evening.
"I'm really pleased for my players because they believe in themselves. I trust them immensely, they work really hard. You just hope that they can continue to build on that and we're just looking for consistency. I hope this is the start of a really good run for us."
Kermorgant's ill-fated spell with the Foxes is best remembered for his missed penalty in the play-off semi-final defeat to Cardiff two years ago, when he
chipped the ball straight to keeper David Marshall.
However, Powell praised the 31-year-old's display on his first return to Leicester since then, and feels the time has come for everyone to move on.
"I played it down with him," added Powell. "I thought he was immense. He led the line on his own, won numerous headers, took his goal very well.
"He played the game I'd like from him every week - I might have to tell him we are playing Leicester home and away every week."