Patent ID: 7834591

Claim:
A Universal Serial Bus (USB) battery charger comprising: a switching regulator having at least one switching transistor, the switching transistor having a first input and a first output, wherein the first input of the switching transistor is coupled to a USB power source; and a filter having a first input and a first output, wherein the first input of the filter is coupled to the first output of the switching transistor; wherein the switching regulator is configured to receive a USB voltage, and generate a switching signal to a control terminal of the switching transistor, and wherein a switching current and a switching voltage at the output of the switching transistor are coupled through the filter to a battery to generate a filtered current and a filtered voltage to charge the battery, wherein the battery is coupled to the first output of the filter, wherein the filtered current is greater than a first input current into the first input of the switching transistor, and the filtered current is reduced, in a current control mode, as a voltage on the battery increases.