A power control circuit for a hard disk drive (HDD) includes a first control circuit, a second control circuit, a first connector connected to a power supply, the first and second control circuits, and a second connector connected to the first control circuit and the HDD. The power supply outputs a first voltage signal and a second voltage signal to the first and second control circuits via the first connector. The first control circuit converts the first and second voltage signals into a form compatible with a timing sequence of the HDD receiving voltage signals, and outputs the first and second voltage signals to the HDD via the second connector. The second control circuit controls the first control circuit.