Power source control system for electronic device and expansion unit connected thereto

An expansion unit removably connected to a portable computer, comprising:

• a power supply for supplying power to the portable computer;
• a detector for detecting whether the portable computer is connected to the expansion unit;
• and
• a controller for preventing the power supply from supplying power to the portable computer when the detector detects that the portable computer is not connected to the expansion unit.

An expansion unit removably connected to a portable computer, comprising:

• a power switch;
• a power supply for supplying a first power and a second power, the first power being supplied in response to the power switch;
• a detector, supplied with the first power, for detecting whether the portable computer is connected to the expansion unit;
• and
• a controller for permitting the power supply to supply the second power to the portable computer when the detector detects that the portable computer is connected to the expansion unit.

A power supply control method for an expansion unit removably connected to a portable computer, the expansion unit including a power switch, a power supply supplying a first power and a second power, and a detector for detecting whether the portable computer is connected to the expansion unit, comprising the steps of:

• activating the power switch;
• supplying, in response to the activating step, the first power to the detector;
• detecting whether the portable computer is connected to the expansion unit;
• and
• permitting, in response to the detecting step, the power supply to supply the second power to the portable computer.

A power supply control method for an expansion unit removably connected to a portable computer, the expansion unit including a power supply supplying a first power and a second power and a detector detecting whether the portable computer is connected to the expansion unit, comprising the steps of:

• supplying the first power to the detector;
• detecting whether the portable computer is connected to the expansion unit;
• and
• preventing the power supply from supplying the second power to the portable computer when the detecting step detects that the portable computer is not connected to the expansion unit.