| 摘要 |
PURPOSE:To shut off unnecessary power to be detoured from a host side and to surely prevent the generation of malfunction in another integrated element or the like by connecting a power supply to an integrated element for an external interface independently of power supply to the other integrated element or the like. CONSTITUTION:When a power supply for a printer 4 is turned on, 5V voltage is supplied from a low voltage power supply 8 to the other integrated circuit 6 and electronic parts 7 through a conductive part 9. In a power supply 10, 5V voltage is obtained from a voltage source VH such as a motor driving power supply by a Zener diode ZD and supplied to the external interface integrated element 5. When the power supply for the printer 4 is turned off and a host side personal computer is driven, unnecessary power may be supplied from a CPU 2 through a signal line 3. However, the power supply 10 for the integrated element 5 is connected independently of the power supply for the other integrated element 6 or the parts 7 in such a case, so that malfunction due to the enter of unnecessary power is not generated. In addition, the circuit can be simplified and the effect for inexpensive cost can be obtained. |
