Carlyle is expected to file an IPO registration document on Monday stating it is looking to sell 30.5 million units at between $23 and $25 per unit, the source said. The greenshoe option includes 4.5 million more units, the source added.

Road shows for the IPO are due to start this week with the firm's founders -- William Conway, Daniel D'Aniello and David Rubenstein -- set to join the marketing efforts as three teams are dispatched to present to investors, the source said.

Carlyle declined to comment.

Carlyle plans to issue new equity in the offering and its owners will not pocket any cash from the IPO directly. Instead, the proceeds will be used to pay down debt and finance operational needs, acquisitions and new fund commitments.

Carlyle, which has about $147 billion in assets under management, returned a record $19 billion to its fund investors in 2011 and reported a 152 percent year-on-year jump in distributable earnings, as sales of many of the assets in its funds boosted profits.

Most private equity firms haven't fared well in the public markets so far. Blackstone Group LP (BX.N), the world's largest private equity firm, has lost about half its market value since its IPO in 2007, before the financial crisis took hold in the United States.

Oaktree Capital Group LLC (OAK.N), a private equity firm focused on debt investments, sold fewer shares than expected in an initial public offering last week that priced at the bottom of an expected range. It shares ended trading on Friday down 3.5 percent from their IPO price.

(Reporting by Greg Roumeliotis; Editing by Richard Pullin)

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