| 摘要 |
It is difficult to increase consumption current of a bus-powered USB device. In order to solve this problem, a conversion cable for a DC connector and a USB connector is adopted in a USB device provided with a USB cable and a DC connector; a state in which power supply voltage is supplied to two sets of USB cables is detected; and a transistor power supply switch is turned on with a logical product thereof. An identification circuit which raises the potential of ground is incorporated in a USB conversion cable to be distinguished from an AC adaptor. When the AC adaptor is connected, the USB device operates as a self-powered USB device.
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