| 摘要 |
PURPOSE: To realize a power supply switching circuit in which the service life of a battery can be prolonged. CONSTITUTION: A switch means (Q1) is turned on when a voltage detection means (OP1) detects an external power supply voltage (VEXT) lower than a desired level. When the external power supply voltage (VEXT) is lower than a desired level, power is fed from a battery power supply (VBT) to an output terminal (TOUT) through the switch means thus feeding the battery power to the output terminal without passing through a diode means (D2). Since conventional voltage drop due to diode means is avoided, the service life of the battery power supply can be prolonged. |
