"N.E.R.D. is the special thing. You don't just throw that [new music] out there. You take your time and you get it right," he said.
Speaking about his bandmates Sheldon Haley and Chad Hugo, he added: "I'm the luckiest guy in the group. Those guys are super cool."
They last released an album in 2010.
Nothing, which reached number 83 in the UK album chart, featured the single Hot N Fun with Nelly Furtado.
"That's the opportunity the people afford us. It's not like we sell all the records in the world," said Williams.
"We cherish that. We don't abuse it by just throwing anything out.
"We take the right amount of time, the proper amount of time to give the people what they ask us for."
Since then Pharrell has focused on solo material and producing and working with other artists including Kanye West, Justin Timberlake and Daft Punk.
Earlier this year he was nominated for a Grammy for his work on Frank Ocean's Channel Orange album and he is known as a sought-after producer.
"I'm not one to brag about myself. More than anything else I'm appreciative they knock," he said of his recent collaborations.
In July it was announced the rapper had reached one million UK single sales for the second time this year after featuring on Robin Thicke's Blurred Lines.
At the time the only other track to reach the milestone in 2013 was Get Lucky by Daft Punk, on which he also appears.