| 摘要 |
<p>PURPOSE:To permit an external power unit to supply a voltage to a back-up circuit even if it loses capacity as a power source when it is used by providing one diode between the input terminal of the back-up circuit and the output terminal of the external direct current power and providing two diodes between the input terminal of the back-up circuit and the output terminal of a built-in power. CONSTITUTION:If the external power unit 10 is effective, the back-up voltage is supplied to the back-up circuit 6 from the external power through one diode 13, and when the external power unit 10 loses capacity as the power source, or when it potential drops more then a prescribed value compared to the built-in power unit 9, the potential of the built-in power unit 9 is supplied to the back-up circuit 6 through two serial diodes 14 and 15. Namely, the potential is supplied to the back-up circuit 6 by three diodes 13, 14 and 15 without being affected by the state of the external power unit 10, and the back-up action of a micro computer 3 can be continued.</p> |
