Patent ID: 7239536

Claim:
An electronic apparatus, for receiving a first DC power through an adapter or receiving a second DC power from a battery, the electronic apparatus comprising: a circuit, comprising a first power input terminal and a second power input terminal, for receiving the first DC power or the second DC power; a first switch, having a first parasitic diode, the first switch being coupled to the first power input terminal; a second switch, being coupled to the first power input terminal, the second switch coupling the second DC power to the circuit selectively; a fuse, comprising: a first terminal, being coupled to a first voltage terminal of the adapter; and a second terminal, being coupled to the first power input terminal of the circuit through the first switch; and a rectifier, coupled to the fuse, the rectifier comprising: a first polarity terminal, being coupled to the second terminal of the fuse through the first switch; and a second polarity terminal, being coupled to a second voltage terminal of the adapter and the second power input terminal of the circuit, wherein the second polarity terminal has a polarity inverse to the second voltage terminals, wherein when the first switch is turned on, the first DC power is inputted to the circuit, and when the second switch is turned on, the second DC power is inputted to the circuit; wherein when a reverse voltage is inputted from the adapter to the electronic apparatus, a reverse current corresponding to the reverse voltage flows from the rectifier to the fuse through the first switch if the first switch is turned on, or through the first parasitic diode if the first switch is turned off.