A power management circuit includes a regulator circuit, a first frequency compensation circuit, a first switch circuit and a detection circuit. The regulator circuit includes a signal output end. The first switch circuit is turned on in response to an enabled first control signal such that the first frequency compensation circuit is coupled to the regulator circuit. The detection circuit determines whether an output capacitor is coupled to the signal output end, and generates the enabled first control signal to turn on the first switch circuit and connect the first frequency compensation circuit to the regulator circuit when the output capacitor is not coupled to the signal output end. Therefore, the regulator circuit is frequency compensated by the first frequency compensation circuit.