Usb device with internal assisting power

Abstract

An universal-serial-bus external device is connected to an universal-serial-bus port of a computer host and the universal-serial-bus port comprises a positive-power end from which a main current is outputted. The external device includes: a load circuit comprising a positive-power end to which a main current is outputted from the positive-power end of the universal-serial-bus port, wherein a load current, for driving the universal-serial-bus external device, is inputted to the positive-power end of the load circuit; and an assisting-power circuit comprising an output end from which an assisting current is outputted to the positive-power end of the load circuit; wherein the load circuit is only provided by the main current if the load current is lower than a first threshold current; and, the load circuit is provided by both the main current and the assisting current if the load current is higher than a second threshold current.

Dependencies are inferred from the claim text.