Abstract: Disclosed is an electronic device. The electronic device may include a plurality of interfaces each of which is connected to one peripheral electronic device in a wired manner to deliver power to the connected peripheral electronic device, a power supply circuit connected to the plurality of interfaces, and a control circuit including a plurality of pins each connected to one interface to allow the power supply circuit to supply power to the plurality of interfaces. In addition, various embodiments understood from the disclosure are possible.

Abstract: In speed control that is performed within a single operating cycle of a printer, three-level control of ON control, OFF control, and chopper control, is performed in place of the two-level control of ON control and OFF control, to effectively suppress speed variations due to load variations within a single operating cycle, even in small printers provided with DC motors having small output torques. In a printer comprising a DC motor 7, a paper feeding unit 5 that includes a paper feeding roller that uses the DC motor as the driving source, and a printing mechanism unit 2, for printing, in use of the printing mechanism unit 2, onto paper that is advanced by a specific amount by the paper feeding unit 5, an encoder 10 for outputting pulse signals according to the rotation of the DC motor 7 is provided.