| 摘要 |
An object of the invention is to provide a backup battery charging circuit capable of continuing to charge a backup battery to the limit of the voltage drop of a main battery so as to reduce the possibility of data disappearance to an achievable extent. For this purpose, a backup battery charging circuit comprises: a main battery serving as a power supply; a backward current protection diode; a regulator circuit using the main battery as the power supply; a limiting resistor; a backup battery; a switch for performing direct charging from the main battery; and a comparator for determining whether the regulator circuit or the switch is to be used.
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