A power managing system includes a power supply, a first converter, a second converter, and a complex programmable logic device. The power supply outputs a first verification signal and a first power upon the condition that the power supply receives a power supply on signal from a motherboard. The first and second converters convert the first power to a second power, a third power, and output a second verification signal, a third verification signal respectively. The complex programmable logic device outputs an enable signal to the motherboard to make the motherboard receive the first, the second, and the third powers upon the condition that the complex programmable logic device receives the first, the second, and the third verification signals.