| 摘要 |
PROBLEM TO BE SOLVED: To prolong the available time of a primary battery used as a battery, enabling power supply from the battery, when an external power supply is not connected and releasing the ground to prevent the battery from being charged, when the external battery is connected. SOLUTION: A power supply circuit comprises external power supply input terminals (2), to which an external power supply is connectable, and battery input terminals (3), to which a battery is connectable. Thus, the power supply circuit supplies power from the external power supply or the battery. When the external power supply is not connected, the negative pole side battery input terminal (3b) is grounded, for the purpose of enabling power supply from the battery connected to the battery input terminals. When an external power supply is connected, the ground is released for the purpose of preventing the battery connected with the battery input terminals from being charged from the external power supply. COPYRIGHT: (C)2004,JPO&NCIPI
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