| CPC H02J 9/062 (2013.01) [H02J 7/00712 (2020.01); H02J 2207/20 (2020.01)] | 9 Claims |
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1. A power supply device for providing electric power to a system end, comprising:
a main battery;
a backup battery;
a first charge circuit, coupled to a first supply node, and generating a first control voltage, wherein the first charge circuit selectively receives an AC (Alternating Current) voltage;
a first transistor, wherein the first transistor has a control terminal for receiving the first control voltage, a first terminal coupled to the main battery, and a second terminal coupled to the first supply node;
a second charge circuit, coupled between a midway node and the first supply node, and generating a second control voltage;
a second transistor, wherein the second transistor has a control terminal for receiving the second control voltage, a first terminal coupled to the backup battery, and a second terminal coupled to the midway node;
a switch element, selectively coupling the midway node to a second supply node according to a third control voltage; and
a control circuit, monitoring a first supply voltage at the first supply node, wherein the control circuit generates the third control voltage according to the first supply voltage;
wherein each of the first transistor and the second transistor is an NMOSFET (N-type Metal Oxide Semiconductor Field Effect Transistor).
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