TCP Capital Corp. late Thursday said that it has commenced a public offering of 3.75 million shares of its common stock, proceeds of which will be used to pay down its revolving credit facility.

The Santa Monica specialty finance company invests primarily in the debt of middle-market companies, including senior secured loans, mezzanine debt and bonds. It now has 31 million shares outstanding and a market cap of $517 million.

TCP also sold shares in May and late September, also to pay down its credit line. The September offering was for 4.37 million shares, with net proceeds of $66.5 million, according to regulatory filings.

The company expects to grant the underwriters a 30-day option to purchase up to an additional 562,500 shares. Deutsche Bank Securities Inc., Raymond James & Associates Inc., Keefe Bruyette & Woods, Inc. and RBC Capital Markets are joint book-running managers for the offering, with Oppenheimer & Co. Inc. the lead manager.

Shares closed down 8 cents, or less than 1 percent, to $16.49 on the Nasdaq.