Best Buy Co. founder and chairman emeritus Richard Schulze will sell an undisclosed amount of stock over a six-month period, according to documents filed with the Securities and Exchange Commission.

Shares in Best Buy fell about 1.5 percent in early trading Tuesday in reaction to Monday's disclosure.

Schulze, who owns more than 70 million shares, or 20 percent of the world’s largest consumer electronics retailer, will reduce his holdings over predetermined times between October and next March. The sales, the first time Schulze has sold Best Buy stock in six years, will be sold in varying amounts on the open market at prices subject to an undisclosed minimum price threshold.

Under the plan, Schulze will have no control when the stock gets sold, a tactic designed to prevent company insiders from trading on nonpublic material information.

The sale “is part of his personal long-term strategy for asset diversification and liquidity,” the SEC filing said.

A company spokesman declined to comment. A source close to the situation said the founder wants to use the money to strengthen the balance sheet of his family foundation, which will focus on K-12 education and medical research.

“He has made very clear his desire to fund his nonprofit Family Foundation and initiate funding to the founders’ updated estate plan,” the source said.

It isn’t clear how many shares Schulze will ultimately sell. But the founder, Best Buy’s largest shareholder, previously told the Star Trib­une that he plans to gradually expand the size of his $100 million family foundation to about $1 billion. Hitting that goal exclusively through stock sales would require a significant reduction in his ownership stake, currently valued at $2.5 billion.

“Our family is feeling good about this,’’ Schulze previously told the newspaper. “And I’m prepared to make meaningful contributions. This foundation will be driven by our research … and finding ways to transform [health and education] for the benefit of mankind.”

David Strasser, a retail analyst with Janney Capital Management, said it makes sense for Schulze, who turns 73 next year, to start selling now. Since December, Best Buy shares have more than tripled, closing Monday at $35.81.

“It’s probably time,” Strasser said. “The foundation is a big part of his life now.”

Last year, Schulze waged a public battle to reclaim control of the company through a private buyout. Only by going private could the founder, along with former executives Brad Anderson and Al Lenzmeier, rescue the struggling company, Schulze had said.

But Schulze ultimately abandoned his bid and expressed support for CEO Hubert Joly and his management team.

“We have a healthy engagement with Hubert and speak with him two or three times a week,” Schulze previously said. “We’re feeling good about our place and space at Best Buy.”