Mobile phone chip supplier Qualcomm on Friday won a legal victory against iPhone maker Apple, with a jury in federal court in San Diego finding that Apple owes Qualcomm about $31 million for infringing three of its patents.

Qualcomm last year sued Apple alleging it had violated patents related to helping mobile phones get better battery life. During an eight-day trial, Qualcomm asked the jury to award it unpaid patent royalties of up to $1.41 per iPhone that violated the patents.

The $31 million penalty is small change for Apple, the second most valuable U.S. company after Microsoft Corp. with a market value of $866 billion and annual revenue totaling hundreds of billions of dollars. But the setting of a per-phone royalty rate for Qualcomm's technology gives the chip supplier a fresh line of attack in its two-year old legal battle with Apple.