Abstract: A power detection method applied to a peripheral apparatus is provided. The method includes the following steps. First, a power signal is received from a data communication interface. Next, it is determined that whether the power signal is able to drive a main function device of the peripheral apparatus. Then, according to the determination result, the power signal is selectively provided to the main function device to drive the main function device.

Abstract: A power detection method applied to a peripheral apparatus is provided. The method includes the following steps. First, a power signal is received from a data communication interface. Next, it is determined that whether the power signal is able to drive a main function device of the peripheral apparatus. Then, according to the determination result, the power signal is selectively provided to the main function device to drive the main function device.

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.