| 摘要 |
PURPOSE: A portable electronic device is provided to switch power with a simple structure, and prevent a failure when the portable electronic device downloading/uploading data by connecting to a communication port of a computer uses the power supplied from the communication port and an installed battery. CONSTITUTION: A Vbus line connects to a power terminal of the communication port and a power terminal of a battery unit. A power line supplies the power inputted to the Vbus line to an electronic circuit in a system main body when a switch is pushed by a projection. A voltage detector(10) searches the voltage of the power inputted to the Vbus line and outputs a comparison result by comparing the detected voltage with the preset voltage. A voltage regulator(20) outputs the power of the Vbus line if the voltage of the Vbus line is higher than the preset voltage, and outputs no power if not. Voltage down diodes(41,42) down the output voltage of the voltage regulator to an operation voltage of the system main body.
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