| 摘要 |
PURPOSE:To prevent the operation of a radio equipment from being interrupted even if the impression voltage of an external power supply is turned to zero due to any failure when the radio set including a secondary battery in itself is driven by the external power supply. CONSTITUTION:A power supply device 10 is provided with a constant voltage power supply circuit 11 for driving the radio equipment, a constant current power supply circuit 12 for charging and a control circuit 13 for stopping the output of the circuit 12 when the output voltage of the circuit 11 is turned to zero. When the device 10 is inserted into the connector 4 of the radio equipment 1, a switch 6 is opened, a radio equipment circuit 2 is driven by the external power supply and a built-in battery 3 is charged. When the output voltage of the circuit 1 is turned to zero, the source-drain of an FET 7 is turned to a conductive state and the voltage of the battery 3 is impressed to the circuit 2. |
