| CPC H02J 9/06 (2013.01) [H02J 7/0063 (2013.01); H02J 7/007182 (2020.01)] | 10 Claims |

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1. A backup power supply charged by a rectifier for suppling power to a load device, the load device being operated with power supplied from the rectifier outputting power of a predetermined voltage, and the backup power supply supplying power to the load device when the power supplied from the rectifier to the load device is insufficient, the backup power supply comprising:
a secondary battery configured to be charged with power from the rectifier;
a control unit configured to control charging and discharging of the secondary battery; and
an output voltage detection unit configured to detect an output voltage from the rectifier,
wherein the control unit is configured to:
control charging the backup power supply by the rectifier; and
stop charging of the backup power supply when the output voltage from the rectifier drops to or below a charge cutoff threshold voltage lower than the predetermined voltage but higher than a discharge threshold voltage lower than the charge cutoff voltage.
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