A power circuit includes a power transistor and a driving circuit. The power transistor draws a power current from a loading node according to a voltage of a driving node and stops drawing the power current according to an over-current signal. The driving circuit includes a high-side transistor, a low-side transistor, a charge pump, a pre-driver, and a desaturation circuit. The high-side transistor provides a supply voltage to the driving node according to a high-side voltage of a high-side node. The low-side transistor couples the driving node to the ground according to a first internal signal. The charge pump generates a high-side voltage that exceeds the supply voltage according to the first internal signal. The pre-driver generates the first internal signal according to a control signal. The desaturation circuit determines that the power current exceeds a threshold to generate the over-current signal.