An AC-to-DC power supply apparatus and a power control structure and method thereof are provided. The provided method includes: making an AC-to-DC converter in the AC-to-DC power supply apparatus convert an AC input voltage in response to a driving signal, so as to generate a DC output voltage; sampling a rectified voltage relating to the AC input voltage, so as to provide a sampling signal; providing an output feedback signal relating to an output of the AC-to-DC converter; multiplying the sampling signal by the output feedback signal, so as to provide a product signal; performing a signal modulation on the product signal, so as to generate the driving signal to control a switching of a main power switch in the AC-to-DC converter; and performing an amplitude-limiting process on the sampling signal or the product signal.