| 摘要 |
PROBLEM TO BE SOLVED: To provide a device which is capable of obtaining power from two or more power supplies.SOLUTION: A switching circuit includes a backup battery and a switching transistor which connects to both a primary power and an internal power rail. When power is supplied via the primary power, the switching circuit operates in a cut-off state so that a reverse flow of electric current to the backup power supply circuit is prevented and the primary power circuit supplies electric power to the internal electric power rail. WHen the primary power circuit is separated or suspended, voltage which is supplied to a gate/control terminal of the switching circuit declines and the switching circuit automatically switches the internal power rail to other energizing state by the backup power circuit.SELECTED DRAWING: Figure 1 |
