| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a power-switching device for feeding power from a battery or an external power supply to an all-time operation system so that the operation life of the battery can be extended. SOLUTION: A power-switching device 421 can automatically send power from a battery 430 or an external power supply VCC to an all-time operation circuit 410. When the external power supply VCC is connected, the switching circuit 421 directs the external power supply VCC to the all-time operation circuit 410, when the connection of the external power supply VCC is disconnected, the switching circuit 421 sends power from the battery 430 to the all-time operation circuit 410. Since the conventional diode connection is replaced by the switching 421, the voltage drop on a diode due to forward bias is avoided. As a result, the battery 430 can be operated, even if a voltage level is low by that amount, and the operation life of the battery 430 can be extended.</p> |
