| 摘要 |
<p>PROBLEM TO BE SOLVED: To secure power supply to a connected USB(universal serial bus) device even when the power source is OFF and maintain its operation state by placing the USB device by a host power source which is provided through a hub port connected to a host if the power supply by a power supply part is stopped. SOLUTION: A power switch 91 outputs a switch state signal indicating the ON/OFF state of external power supply to the power supply part 16. A power source detection part 92 detects the state of the power supply by the power supply part 16 and outputs a supply detection signal. A logic circuit part 93 logically operates those switch state signal and supply detection signal. A.power switch part 92 selects the power supply in respeonse to the circuit part 93, by the power supply part 16 or the host power supply by the hub port UP1 connected to the host and sends electric power to a USB control part 62 and hub ports DP1 to DP3 connected to peripheral equipment.</p> |
