AC-to-DC power supply apparatus and power control structure and method thereof

A power control method, adapted to an AC-to-DC converter, the power control method comprising:

• making the AC-to-DC converter 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 under an continuous current mode (CCM) or an boundary current mode (BCM);
• and
• performing an amplitude-limiting process on the sampling signal or the product signal, so as to limit a peak voltage level of either the sampling signal or the product signal at a constant voltage, wherein an output of the amplitude-limiting process is equivalent to the sampling signal if either the sampling signal or the product signal is less than the constant voltage, while the output of the amplitude-limiting process is equivalent to the constant voltage if either the sampling signal or the product signal is greater than the constant voltage.

A power control structure, adapted to an AC-to-DC converter, the power control structure comprising:

• a sampling circuit, configured to sample a rectified voltage relating to an AC input voltage of the AC-to-DC converter, so as to provide and output a sampling signal;
• an output feedback circuit, configured to provide and output an output feedback signal relating to an output of the AC-to-DC converter;
• a multiplying circuit, configured to multiply the sampling signal by the output feedback signal, so as to provide and output a product signal;
• a signal modulation circuit, configured to perform 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 under an continuous current mode (CCM) or an boundary current mode (BCM);
• and
• an amplitude-limiting circuit, coupled between the sampling circuit and the multiplying circuit or between the multiplying circuit and the signal modulation circuit, and configured to perform an amplitude-limiting process on an output of the sampling circuit or an output of the multiplying circuit, so as to limit a peak voltage level of the output of either the sampling circuit or the multiplying circuit at a constant voltage, wherein an output of the amplitude-limiting circuit is equivalent to the sampling signal if the sampling signal of the output of either the sampling circuit or the multiplying circuit is less than the constant voltage, while the output of the amplitude-limiting circuit is equivalent to the constant voltage if the sampling signal of the output of either the sampling circuit or the multiplying circuit is greater than the constant voltage.