| 摘要 |
<p>PROBLEM TO BE SOLVED: To drive a connected load normally even during exchange of an external battery. SOLUTION: A power supply circuit 10 comprises a primary battery (external battery) 12 which drives a connected load 16, a secondary battery (built-in battery) 18 which drives the connected load in place of the external battery, a voltage detection means 40 which detects a terminal voltage of the eternal battery, a primary switch 20 which controls an electric power supply path of the built-in battery based on an output Cb of the voltage detection means, an overcharge preventing means 30 which prevents the overcharge to the built-in battery by the external battery, and a switch 26 which is connected to a charge path to the built-in battery and is controlled by an output Ca of the overcharge preventing means. When the external battery voltage is dropped below the specified voltage, the connected load is driven by the built-in battery turning on the switch 20 using the output Cb. Thereby, while the external battery is changed, the normal driving voltage is continued to be supplied to the connected load from the built-in battery, the connected load can be driven in normal even during battery exchange and operation continues without interruption.</p> |
