Digital camera selectively powered by an internal and an external power supply

A digital camera for photographing a subject to output image signals representing the subject, comprising:

• an interface connectable to an external data processing device, the interface transferring the image signals to the data processing device;
• an internal power supply for supplying a first power to components of said digital camera;
• an external power receiving circuit for receiving a second power from the data processing camera;
• a first switching circuit for selectively switching between said internal power supply and said external power receiving circuit to supply the first or the second power to the components of said digital camera;
• a connection detection circuit for detecting that the data processing device has been connected to said interface;
• and
• a control circuit for controlling said first switching circuit in response to said connection detection circuit,
• wherein said control circuit controls said first switching circuit in such a way that, when said connection detection circuit does not detect that said interface is connected to the data processing device, the first power is supplied to the components of said digital camera, and when said connection detection circuit detects that said interface is connected to the data processing device, said internal power supply is disconnected and the second power is supplied to the components of said digital camera, and
• wherein said internal power supply comprises a secondary battery, and said digital camera, further comprises an adapter connector for connecting a charging adapter to charge said secondary battery by a commercial power supply, a charging circuit for charging said secondary battery, and a second switching circuit for charging said secondary battery selectively through said charging circuit or through the charging adapter via said adapter connector, the charging adapter connected to the secondary battery without passing through the charging circuit.